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date: 21 July 2017

Inoculation Theory Applied in Health and Risk Messaging

Summary and Keywords

Referred to as the “most consistent and reliable method for conferring resistance to persuasion” by Miller et al. in 2013, over the past 50 years inoculation has exerted significant influence in shaping theoretical and contextual resistance research and message design. Used as a message strategy, inoculation elicits threat, or realized attitudinal/behavioral vulnerability, which motivates individuals to shore up attitudinal/behavioral defenses by providing both material and guided practice aiding the process of effective counterarguing, which in turn increases individuals’ resistance to attitudinal/behavioral challenges. The motivation is responsible for sustaining the inoculation effect over an extended period of time. Inoculation messages, however, do much more than just inspire a robust defense. They motivate individuals to engage others regarding the attitudinal/behavioral topic in an attempt to reassure and advocate their positions, thus diffusing the inoculation message over social networks. The attitudinal/behavior protection elicited by inoculation messages is not limited to the message’s target attitude/behavior, but instead spreads over related attitudes/behaviors as well, thus increasing the pragmatic utility of this message strategy. Inoculation’s effectiveness extends beyond the realm of resistance, as inoculation messages are also effective in both shaping and changing attitudes/behaviors.

Because of its success, inoculation-based message strategies have been applied in numerous contexts and with numerous topics. Some of inoculation’s applied contexts include commercial, instruction/education, interpersonal, political, corporate, public relations, cross-cultural, health, and risk. More specifically, in the health and risk contexts, inoculation has been applied in promotion or prevention capacity on topics such as politically-motivated violent acts, smoking, drinking, unprotected sex, vaccination, and health-related policy, with current research exploring its efficacy in addiction interventions and indoor tanning-bed usage prevention. Inoculation may also be used as a strategy to reduce recidivism in criminal prison inmates and preventing verbal aggression in schools. Additional promising areas for application of inoculation-based strategies may include the promotion and protection of healthy eating habits as well as positive attitudes/behaviors toward mammograms, colonoscopies, breastfeeding, and regular exercise, just to name a few. As Ivanov suggested, the “application of the strategy [is] boundless.”

Keywords: inoculation theory, resistance, persuasion, social influence, message design, message processing, health, risk, health and risk message design and processing

The Origins of Inoculation Theory

Although it traces its origin to ancient Greek rhetoric, inoculation theory scholars attribute the inspiration for the theory to the seminal work of Lumsdaine and Janis (1953) on two-sided messages (see Ivanov, 2012; Pfau, 1992) and the “unanticipated finding” (Pfau, 1992, p. 27) evidencing the effectiveness of these messages in conferring resistance to subsequent attitudinal challenges. Lumsdaine and Janis attributed the success of two-sided messages, which present arguments from both sides of the issue, to their inoculating function as suggested in the authors’ report:

But if the initial communication is, instead, a two-sided one it will already have taken into account both the positive and negative arguments and still reached the positive conclusion. When the listener is then subsequently exposed to the presentation of opposing arguments in the counterpropaganda, he is less likely to be influenced by them. He is not only familiar with the opposing point of view, but has been led to the positive conclusion in a context in which the negative arguments were in evidence. In effect, he has been given an advance basis for ignoring or discounting the opposing communication and, thus “inoculated”, he will tend to retain the positive conclusion.

(p. 318, bold added for emphasis)

Indeed, it is the inoculating function of two-sided messages that inspired McGuire to propose the original core mechanisms of the theory (McGuire, 1964). His work has stimulated five and a half decades of vigorous programmatic research on inoculation-elicited resistance (Compton, 2013). During that time, the original theoretical mechanisms—threat and counterarguing—proposed by McGuire (1964) as responsible for the generated resistance process have been tested (e.g., Ivanov, Pfau, & Parker, 2009b), challenged (e.g., Banas & Rains, 2010), nuanced (e.g., Miller et al., 2013), and complemented (e.g., Pfau et al., 2003).

In addition, inoculation theory, “the grandparent theory of resistance to attitude change” (Eagly & Chaiken, 1993, p. 561), has been applied to numerous communication contexts including commercial (e.g., Ivanov, Pfau, & Parker, 2009c; Pfau, 1992), instruction/education (e.g., Compton & Pfau, 2008), interpersonal (e.g., Sutton, 2011), political (e.g., Compton & Ivanov, 2013), corporate (e.g., Dillingham & Ivanov, 2015); public relations (e.g., Wan & Pfau, 2004), cross-cultural (e.g., Ivanov, Parker, Miller, & Pfau, 2012b), health (e.g., Parker, Ivanov, & Compton, 2012) and risk (e.g., Ivanov et al., 2016). Each of these efforts, both theoretical and contextual, has contributed to our understanding of the resistance-based processes unleashed by inoculation, which, in turn, has enriched our knowledge base relied upon in designing effective inoculation-based message strategies.

This chapter first discusses inoculation’s boundaries and the theory’s original mechanisms, testing, and logic as offered by its original author, William McGuire. It then addresses additional complementing and/or competing variables associated with the inoculation-based process(es) of resistance derived from four decades of inoculation research since McGuire’s original work. The theoretical discussion is followed by brief summaries of the theory’s application into several communication contexts. Consistent with the topics in this volume, the primary contextual focus is on the design and processing of effective inoculation messages applicable in health and risk communication situations. In addition to summarizing the inoculation work in these areas, through an example, this chapter provides a recommendation on how to design an effective inoculation message. Although the example will be specific to the context of health and risk communication, it is nevertheless applicable in any context consistent with the theory’s message efficacy. The chapter concludes with a brief discussion about inoculation’s future after considering some of its limitations.

Boundary Conditions

Like most theories, inoculation is not without boundary conditions. Some of these are theoretical (e.g., initial attitude) while others are practical (e.g., involvement). Furthermore, some hold multiple roles in the inoculation process (e.g., involvement as boundary condition, moderator, and mediator). This chapter focuses on the most relevant boundary conditions of the theory: initial attitudes, involvement, and cross-protection (blanket or umbrella protection).

Initial Attitudes

Consistent with the medical (or biological) inoculation analogy, McGuire believed that inoculation should be used to protect healthy (previously unchallenged) beliefs (1964). Medical (or biological) inoculations are used to protect healthy individuals from succumbing to a viral infection. As Ivanov and colleagues pointed out, “McGuire’s (1964) use of the biological analogy was not merely stylistic, it was explanatory” (Ivanov et al., 2015, p. 220). As such, attitudinal inoculation should be used to protect individuals with healthy (or established) attitudes from succumbing to a counter-attitudinal challenge. Thus, the boundary condition here-imposed by the medical (or biological) analogy suggests that the attitude in place must be healthy (already established) for inoculation to be an appropriate strategy. Consequently, the application of inoculation is theoretically (or analogically) limited to protecting already-established attitudes (beliefs, behaviors, values, etc.). That is not to suggest that this strategy is ineffective as an approach to change or shape attitudes. In fact, studies have shown that inoculation messages can have a desired effect when used for individuals with neutral and opposed (or unhealthy) attitudes as well (Ivanov et al., 2017; Wood, 2007). However, in such cases, inoculation simply functions as a two-sided attitude formation or attitude change persuasive strategy, rather than as a preemptive attitude protection resistance strategy (Ivanov et al., 2017). If rigidly bound to the medical (or biological) analogy, inoculation is a preemptive attitude protection strategy, which requires that the attitude is established before it can be protected.


Pfau and colleagues believed that “involvement holds the key to inoculation’s terrain” (1997, p. 210). In their study, these authors discovered that inoculation works best with moderately-involving issues. They reasoned that low-involving issues would fail to generate a threat—the requisite component of inoculation (Compton & Pfau, 2005)—because people will not care enough about these issues to be properly motivated to protect them. On the other hand, highly-involving issues should be so important to the individuals that they would not necessitate additional motivation. Given the high importance of the issue, these individuals have prior (or inherent) motivation to defend the issue and likely have already prepared their defenses in anticipation of attitudinal challenge. Thus, according to Pfau and colleagues (1997), inoculation would have the greatest contribution to resistance with moderately-involving issues. However, although the results of Banas and Rains’ (2010) meta-analysis showed patterns consistent with Pfau et al.’s findings, the results were not statistically significant; thus no curvilinear relationship for involvement was detected. Banas and Rains speculated that their findings could be influenced by a lack of power associated with the test performed. Alternatively, they suggested, the lack of significant findings could be the result of how involvement has been operationalized in previous inoculation studies, which mainly has consisted of embedding involvement in the topic rather than experimentally manipulating it in the messages. As a result, the notion that issue involvement creates a boundary condition for inoculation has to be considered with reservation.


One of inoculation’s main advantages, further discussed in the next section, is the ability to motivate individuals to defend their attitudes (McGuire, 1964). The motivation ensures that individuals do not solely rely on the content of the inoculation message for protection against forthcoming attitudinal challenges. Instead, motivated individuals go a step further by identifying new challenges they proceed to refute and by increasing their ability, via counter-attitudinal practice, to defend against challenges not previously encountered. Stated differently, inoculation forms an umbrella (or blanket) of protection against all arguments within an issue domain (Banas & Rains, 2010; Compton & Pfau, 2005; McGuire, 1964).

Recently, however, Parker and colleagues (2012, 2016) argued that the umbrella (or blanket) of protection may span much wider than originally thought. The authors suggested that inoculation used to protect a single attitude may provide cross-protection for different but related attitudes, as well. The support for their prediction comes from the use of vaccinations in medical settings where a vaccine used to generate protection against one virus can create protection against multiple viruses (Clemens et al., 1988). The results of a few recent studies provided early support for this prediction (Ivanov et al., 2015; Parker et al., 2012; Parker, Rains, & Ivanov, 2016), thus extending the boundaries of the theory.

This section of the chapter identified the terrain in which inoculation operates. The next section focuses on the mechanisms that drive the inoculation-elicited process of resistance.

Original Mechanisms, Processes, Testing, and Logic

The inspirational work of Lumsdaine and Janis (1953) demonstrated that two-sided messages can be effective in protecting attitudinal slippage against subsequent counter-attitudinal challenges. However, the mechanisms responsible for the effectiveness of the inoculating message, as proposed by these authors, significantly differed from that of McGuire. Lumsdaine and Janis attributed the success of the two-sided messages in part to the credibility of the source as two-sided message recipients “may be more impressed by the communication and less inclined to distrust the arguments as coming from a biased source if the communicator makes it clear that he has taken the negative arguments into account” (p. 317). In addition, by attributing the fortification of the attitude to careful message scrutiny and deliberation in which the pro-attitudinal arguments have outperformed the counter-attitudinal ones (Petty & Cacioppo, 1986), Lumsdaine and Janis suggested that prior encounters with the counter-attitudinal challenges would lead to “ignoring or discounting the opposing communication” (p. 318). As such, while Lumsdaine and Janis suggested that the message elicits careful content processing in the attitude fortification stage, they also suggested a more heuristic defense process that relied on discounting or ignoring, rather than engaging, the assailing attitudinal challenges.

McGuire (1961, 1964, 1970), conversely, suspected that the defense process of inoculated individuals is much more active than suggested by Lumsdaine and Janis (1953). For an answer regarding the process of attitudinal inoculation-based resistance, he turned to the medical analogy derived from human immunization. McGuire reasoned that the same way healthy people are inoculated from viruses, individuals with established attitudes (beliefs, values, opinions, intentions, behaviors, etc.; henceforth, for convenience, referred to as attitudes) could be inoculated from forthcoming attitudinal challenges. More specifically, just as the introduction of a weakened form of a virus shocks the body into producing antibodies capable of fighting off the viral agent when encountered, McGuire believed that a weakened from of counter-attitudinal arguments can provide a “shock value” (1961, p. 185) in the form of realization that the attitude in place is indeed vulnerable. The shock should motivate the individual to shore up the attitude in place and thus render the individual better prepared and more resistant to forthcoming challenges. An important key to the process was the introduction of weakened counter-attitudinal arguments; but how weak should they be? Drawing again from the medical (or biological) analogy, he reasoned that, akin to vaccines, the arguments needed to be strong enough to provide a shock to the system, but not so strong as to overwhelm it. As a result, McGuire’s “use of the biological analogy was not merely stylistic, it was explanatory” (Ivanov et al., 2015, p. 220; but also Compton, 2013; Compton & Pfau, 2005).

McGuire (1961, 1964, 1970), McGuire and Papageorgis (1962), and Papageorgis and McGuire (1961) identified two key mechanisms that are responsible for the effectiveness of inoculation messages: threat and counterarguing. Threat, as McGuire (1964) believed, provides the motivation for individuals to defend their attitudes. The defense process consists of individuals enhancing their ability to counterargue conflicting viewpoints through counterarguing practice. This counterarguing practice, according to McGuire (1964), is motivated by threat, supported by the material (content) presented in the inoculation message, and aided by the exemplification of an effective counterarguing exercise offered in the message. Thus, in short, inoculation elicits threat, which motivates counterarguing, which in turn generates greater attitudinal resistance.


In McGuire’s work, threat—the shock value of the message—was generated by presenting individuals with weakened counter-arguments displaying the potential vulnerability of the attitude. Hence, threat represented a realization of attitudinal vulnerability (Compton & Pfau, 2005). In McGuire’s (e.g., McGuire, 1961) initial work, threat was ostensibly generated simply due to the presentation of weakened counter-attitudinal arguments. McGuire termed this implicitly generated shock value as “inherent threat” (McGuire, 1970, p. 63). In his subsequent work (e.g., McGuire & Papageorgis, 1962), he introduced an explicit form of threat as well by using a forewarning in the message. The forewarning, rather explicitly, instructed individuals that their attitudes were vulnerable to forthcoming challenges. Consequently, the combination of explicit and implicit (or inherent) threat, McGuire believed, was responsible for unlocking defense motivation in the individual, which was pivotal in inspiring defense building and practice. As such, McGuire believed that threat is a “requisite construct within the process of inoculation” (Miller et al., 2013, p. 128; but also see Compton & Pfau, 2005). More contemporary inoculation scholars agree with McGuire’s assessment of threat’s importance in inoculation-based resistance (Compton, 2013; Compton & Pfau, 2005; Ivanov et al., 2012b; Miller et al., 2013; Pfau, 1995); this sentiment was punctuated by Pfau’s assertion that threat is “the most distinguished feature of inoculation” (1997, p. 137).

Without threat, the effect of inoculation would be limited to the one prescribed by Lumsdaine and Janis (1953). To remind, these authors believed that the inoculating success of two-sided messages rests, in part, with the familiarity of the forthcoming counter-attitudinal arguments, due to their prior encounter in the two-sided message. In that context, the individual would be more likely to ignore or discount the assailing challenge as one that has already been dealt with and overcome. Thus, the effectiveness of inoculation messages would be limited to scenarios in which the individual faces the same counter-attitudinal arguments previously encountered. However, the effect would be much less pronounced, if at all present, when the counter-attitudinal arguments are novel i.e., have not been faced before. McGuire (1964) argued that threat motivates individuals to shore up their defenses and not only rely on the counter-attitudinal arguments previously encountered in the inoculation message. To show that inoculation’s threat-generated motivation, rather than content, is primarily responsible for the effectiveness of inoculation messages, McGuire (1964) rendered inoculated individuals to either the same counter-attitudinal challenges encountered in the inoculation message or a set of different ones. His general findings and conclusions, supported by a recent meta-analysis (Banas & Rains, 2010), confirmed McGuire’s suspicion as no appreciable difference in the effectiveness of inoculation was discovered based on whether attacks featured the same or novel content. Thus, it seems, the motivation generated by threat, rather than the content of the inoculation message, is largely responsible for the effectiveness of inoculation. This finding has practical significance as well because it suggests that in order to use inoculation messages, one does not have to counter all possible arguments on the issue at hand because inoculation creates an umbrella protection that is capable of “safeguarding against both those counterarguments addressed . . . [by the inoculation message] . . . and those not addressed” (Pfau, 1995, p. 101; also see Banas & Rains, 2010).

Yet, in spite of its ascribed importance, threat remained a primitive construct until the late 1970s when a scale to directly measure threat was developed (Burgoon, Cohen, Miller, & Montgomery, 1978). Numerous subsequent inoculation studies have confirmed the role of threat in the process of resistance (e.g., Ivanov et al., 2012b; Miller et al., 2013; Pfau et al., 2004); however, a recent meta-analysis by Banas and Rains (2010) failed to validate these findings even though the results were in the expected direction. The authors speculated that low power of the test might be responsible for the results. Another possible reason for this inconsistency may be tied to the measure used to assess the presence of threat. A closer examination of previous inoculation studies assessing threat suggests a limited range of threat scores clustered around the midpoint (Compton, 2013). The question inoculation scholars are presently attempting to answer is whether this result is an artifact of the measure (i.e., lack of sensitivity) or the ability of scholars to enhance the level of generated threat. For example, Pfau and colleagues (2010) incorporated components of vested interest (Crano & Prislin, 1995) in their attempt to portray the threat as more “personally relevant” (p. 4). Their attempt was not successful as their enhanced threat manipulation (M = 3.39) was statistically undifferentiated from the regular threat manipulation (M = 3.41) on a seven-point scale. Based on an earlier work by Burgoon and colleagues (1976), Ivanov and colleagues (2013b) manipulated threat by varying the certainty with which the attack is likely to occur. Although the authors had some manipulation success, they were still unable to raise the level of threat beyond the midpoint on a seven-point scale (highest M = 3.88). Finally, Miller and colleagues (2013), borrowing from the theory of psychological reactance (Brehm, 1966), manipulated threat as a restriction to the freedom of individuals to hold the desired attitudes. Although the study was successful in manipulating threat, the highest level of generated threat did not reach the midpoint mark (M = 3.88) on the seven-point traditional scale.

Threat may indeed be a requisite for inoculation-based resistance (Compton & Pfau, 2005; but see Banas & Rains, 2010); however, scholars have much work to do to better understand how to significantly manipulate and better assess this variable. If threat motivates defense preparation (Compton, 2009; Ivanov et al., 2009b; McGuire, 1964), then enhancing threat may be an important factor in eliciting significant motivation.

Yet, the relationship between threat and motivation in the inoculation-elicited resistance is theoretical. The notion that enhanced threat leads to greater motivation is assumed, but unconfirmed. For example, Compton and Ivanov acknowledged this limitation in their study suggesting the “assumption is that threat . . . elicits motivation to engage in resistance processes, such as counterarguing . . .; however, [they] did not measure motivation in this study” (2012, p. 11). Thus, even though motivation seems to be identified as a key mediator of generated resistance, motivation has never been explicitly established nor incorporated into the inoculation model. Its presence has been inferred by inoculation scholars as being elicited by threat and contributing to defense bolstering. For example, McGuire suggested that “any extrinsic threat . . . should increase . . . motivation to assimilate the material and hence enhance its immunizing effectiveness.” (McGuire, 1964, p. 210, italics added for emphasis). Compton added that “. . . both inherent and explicit threat affects motivation to attend to the information presented in inoculation messages” (Compton, 2009, italics added for emphasis). Ivanov and colleagues stated that “the threat element warns the individual about the vulnerability of the attitude currently in place. This realized vulnerability acts as a motivator for the individual to seek out information that would strengthen his or her current attitude” (Ivanov et al., 2009b, p. 48, italics added for emphasis). Thus, motivation is implicitly assumed to be the catalyst for defense bolstering, but could motivation be generated independent of threat? How much of the variance in motivation is explained by threat compared to other mechanisms (e.g., anger, involvement, etc.)?

Threat continues to be a focal point in inoculation research (see Compton, 2013). However, much more remains to be learned about this variable and its interaction with motivation and other components of the inoculation-based process of resistance.


The second original mechanism of inoculation-elicited resistance, according to McGuire (1964), is counterarguing. Consistent with the biological analogy, counterarguing against opposing counter-attitudinal challenges is analogous to a human body fending off a viral infection by producing antibodies. Compton defines this concept as a process that includes “the collective generation of counterarguments and refutations, [and] post-inoculation pretreatments” (2013, p. 222). McGuire believed that inoculation messages generate threat, which in turn motivates the process of defense bolstering, which he believed to be in the form of counterarguing. As such, McGuire’s vision of inoculation differs from that of Lumsdaine and Janis (1953). McGuire, believed that motivated counterarguing of opposing viewpoints is the mediating process of inoculation resistance, rather than the discounting or ignoring of opposing arguments or viewpoints. This process, according to inoculation scholars (e.g., Pfau et al., 2004), was generally assumed to be an intrapersonal or internal “subvocal, psychological process” (Brandt, 1979, p. 324). However, more recent work has suggested that the process of counterarguing may also be interpersonal as inoculated individuals may turn to others within their social networks, seeking attitudinal reassurance or practicing attitudinal advocacy (Compton & Pfau, 2004, 2009; Ivanov et al., 2012a, 2015).

Unlike threat, which remained as a primitive term in McGuire’s studies, counterarguing received a single assessment as participants were asked to list all of the arguments that came to mind in favor of the belief (see Papageorgis & McGuire, 1961). The quality of the arguments were subsequently rated by a trained outside professional; however, no differences were discovered between the inoculation and control groups, thus failing to confirm the process of inoculation as envisioned by McGuire. Smith suggested that “McGuire provided no evidence that his motivational and informational pretreatments . . . increased the ability and willingness of people to counterargue persuasive attacks” (1982, pp. 294–295). Compton and Pfau (2005) also conceded that the evidence on counterarguing was not as definitive, which is consistent with studies discovering inoculation-generated resistance in absence of significant counterarguing effect (e.g., Compton & Ivanov, 2012). Ivanov, Parker, and Dillingham attributed the equivocality of the findings, at least in part, to the methods used to capture counterarguing (2013a). After pointing out the strengths and weaknesses of several techniques used in measuring counterarguing, the authors suggested using a combination of measures to capture counterarguing by pointing to successful studies that have applied this approach (Banas & Bessarabova, 2009; Miller et al., 2013).

While, as suggested by Compton and Pfau (2005), the evidence may not be definitive, that is not to suggest that evidence of counterarguing mediating the inoculation process or resistance is lacking (e.g., Pfau et al., 2005). In fact, a significant number of studies have found support for McGuire’s theoretical mechanisms regardless whether counterarguing was treated and assessed as a subvocal (e.g., Ivanov et al., 2009a; Pfau et al., 1997, 2001, 2004) or a vocal (e.g., Ivanov et al., 2015) process.

Treating counterarguing as a vocal, in addition to a subvocal, process, a relative novelty in inoculation research, was first suggested in Compton and Pfau’s (2009) seminal article on inoculation and word of mouth communication. In their theoretical essay, the authors proposed that inoculated individuals, in addition to engaging in the process of subvocal counterarguing as prescribed by McGuire (1964), may also engage in conversations with other individuals for the purpose of reassuring their current position on the topic and/or advocating their position to others. Empirical tests by Ivanov and colleagues (2012a, 2015) have subsequently confirmed the reassurance and advocacy functions of post-inoculation word-of-mouth communication, termed as post-inoculation talk (PIT) (Ivanov et al., 2012a, 2015). As a collection, their findings showed that PIT, boosted by inoculation-elicited threat and anger, enhanced attitudinal resistance. A study by Dillingham and Ivanov (2016) partitioned the effects of vocal and subvocal counterarguing and added an additional dependent variable, attitude certainty. The subsequent results revealed a more nuanced interplay between these processes (vocal vs. subvocal counterarguing) and variables (attitude vs. attitude certainty) than originally conceptualized. The process of subvocal counterarguing, when decoupled from vocal counterarguing by restricting the participants from engaging in PIT, yielded familiar findings i.e., inoculation worked in generating attitudinal resistance. However, inconsistent with previous findings (e.g., Pfau et al., 2004), inoculation had no effect on attitudinal certainty. The addition of the vocal (PIT) to the subvocal process of counterarguing, while having no appreciable impact on attitudinal resistance, did have a positive impact on attitudinal certainty. As a result, the authors concluded that, while subvocal counterarguing may be responsible for generating attitudinal resistance, PIT plays an important role in the process of inoculation-elicited resistance by bolstering the certainty with which the attitudes are held, possibly as function of reassurance. An additional benefit of vocal counterarguing or PIT is the ability of the message to be diffused over social networks to individuals not exposed to the original inoculation; thus submitting others to messages of reassurance and/or advocacy. Hence, the effect of PIT in the inoculation process may be quite significant. Yet, while PIT seems to have a positive inoculative effect on the original message recipients, the impact of PIT on those receiving the inoculation message via social diffusion remains unknown and in need for more systematic research.

In general, inoculation works. Over 50 years of research has provided an overall support for the inoculation-elicited process of resistance mediated by the variables—threat and counterarguing—identified by its original author (but see Banas & Rains, 2010). Yet, subsequent inoculation scholarship has identified additional variables (moderating and mediating) impacting the inoculation process of resistance. The next section addresses some of the most relevant complementing and/or competing variables associated with the inoculation-based process(es).

Complementing and/or Competing Processes: Mediators, Moderators, and Outcomes

While agreeing with the role of the original mechanisms in the inoculation process, Insko (1967) suspected that this process, as conceptualized by McGuire, is incomplete. He intuitively believed that additional mechanisms yet to be uncovered complicated the resistance process inspired by inoculation. Decades of research has confirmed Insko’s intuition as additional moderating and mediating variables have been added to the inoculation process of resistance. This section briefly attends to some of the most relevant variables in this process including involvement, self-efficacy, attitude accessibility, associative networks, attitude certainty, affect, message source, gender, modality, message type, and outcomes.


Issue involvement plays a significant role in the process of inoculation-generated resistance as it can moderate, mediate, and function independently of the inoculation process. Defined as the salience or importance for the receiver of an attitude object (Pfau et al., 1997), issue involvement may impact the effectiveness of inoculation. Pfau and colleagues (1997) discovered that moderate levels of issue involvement may produce most pronounced inoculation effects; yet these findings have not received meta-analytic support (Banas & Rains, 2010).

In a different study, Pfau et al. (2010) examined the effects of alternative types of involvement (outcome-relevant, value-relevant, and impression-relevant). They hypothesized that outcome-relevant involvement, which they likened to issue involvement, would confer resistance by influencing the original mechanisms of inoculation-based resistance, threat and counterarguing. In contrast, the authors expected that value-relevant (i.e., an attitude integrally connected to the person’s values) and impression-relevant involvement (i.e., a desire to express socially-supported attitudes by significant others) would bypass the original inoculation mechanisms and generate resistance independent of threat and counterarguing (Pfau et al., 2010). No statistically significant results were discovered for impression-relevant involvement, but both outcome-relevant and value-relevant involvement impacted resistance by bypassing threat and counterarguing. These findings are consistent with the earlier work of Pfau and colleagues (1997) who also discovered issue involvement to impact resistance independent of the traditional inoculation mechanism at each level of involvement: high, moderate, and low. In addition to the independent influence on resistance, moderate level of issue (or outcome-relevant) involvement also impacted threat and counterarguing as hypothesized in the Pfau and colleagues’ (2010) study. Thus, involvement seems to play a significant role in the process of resistance independently and by moderating the effect of inoculation.

Issue involvement also mediates the inoculation-elicited process of resistance. In their study, Pfau and colleagues (2004) discovered that inoculation generated threat, which elicited involvement. The elicited involvement then strengthened attitudinal certainty and accessibility and increased counterarguing level. In turn, counterarguing and attitude accessibility directly and certainty indirectly (through attitude accessibility), impacted resistance.

In conclusion, issue involvement has an instrumental role in the process of inoculation-generated resistance. Initial level of involvement, in general, seems to impact the process of resistance independently of the traditional inoculation processes; however, at moderate levels, it also has a direct positive impact on threat and counterarguing. Issue involvement is also elicited by the inoculation message and, as such, it increases the level of resistance via counterarguing, attitude certainty, and attitude accessibility.


Similar to issue involvement, self-efficacy also plays multiple roles in the inoculation-elicited process of resistance as a moderator and mediator (Compton, 2013). In general, self-efficacy is expected to lower the level of experienced threat as increase in self-efficacy should increase the confidence of the individuals in their abilities to defend the challenged attitude (Pfau et al., 2001). Yet the first study to measure self-efficacy (Pfau et al., 2001) did not discover any definitive impact of self-efficacy on threat. However, it did show self-efficacy to be positively related to happiness and anger, both of which enhanced resistance (2001).

Additional studies tested self-efficacy as a product of inoculation and discovered that inoculation can enhance self-efficacy (Farchi & Gidron, 2010; Ivanov et al., 2016; Jackson et al., 2015; Pfau et al., 2009); however, none of these studies directly assessed the impact of elicited self-efficacy on the attitudes. Thus, much more remains to be learned about the mediating role of self-efficacy in the process of inoculation-elicited resistance.

Attitude Accessibility, Certainty, and Associative Networks

Roskos-Ewoldsen and Fazio (1997) suggested that beliefs that are more readily accessible from memory are more salient and more likely to be considered when confronting an issue. Inoculation enhances the accessibility of these beliefs (Pfau et al., 2003, 2004) and accessibility in turn enhances resistance (Pfau et al., 2004). This process works independently of the original mechanisms of the theory—threat and counterarguing—as well as collaboratively through threat, as threat increases attitude accessibility, which leads to greater resistance (Pfau et al., 2004).

The certainty with which individuals hold the attitude also plays an important role in the inoculation process of resistance (Pfau et al., 2004, 2005). Inoculation treatments directly boost attitudinal certainty, which in turn enhances resistance (Pfau et al., 2004, 2005). In addition, certainty can be boosted by threat and elicited involvement and can impact resistance both directly and indirectly by enhancing attitude accessibility (Pfau et al., 2004).

Besides bolstering attitude accessibility and certainty, inoculation modifies the structure of individuals’ associative networks by adding additional nodes and increasing the number of linkages among nodes (Pfau et al., 2005; but see Pfau et al., 2009). The associative network structures consist of affective and cognitive nodes located in long-term memory that are connected by associative pathways (or linkages). More complex structures consist of more interconnected nodes and, as such, are less vulnerable to challenges (2005). As Pfau and colleagues (2005) discovered, inoculation has the ability to enhance individuals’ associative networks, which increases resistance.


For many years, inoculation theory was considered to elicit primarily a cognitive process of resistance (Compton & Pfau, 2005). Recent inoculation scholarship has recognized the importance of affect in the process of inoculation-elicited resistance (e.g., Compton & Ivanov, 2014; Ivanov et al., 2012a, 2012b; Miller et al., 2013). For example, studies have shown that inoculation can elicit anger (e.g., Ivanov et al., 2012a) or happiness (Pfau et al., 2001), both of which had a positive impact on resistance. But, inoculation can also impact emotions, such as enhancing pride (Pfau et al., 2006) or reducing fear (Pfau et al., 2009). The precise moderating, mediating, and outcome roles specific emotions and moods play in the inoculation process of resistance is not yet clear. Much remains to be learned about the impact of affect on the process of inoculation.

Message Source and Gender

The message source plays a relevant role in the inoculation process. An and Pfau (2004) discovered that more positive perceptions of the credibility of the inoculation source leads to more effective inoculation. Thus, the credibility of the source can moderate the effectiveness of the inoculation message. In addition, a source can have a mediating role in the inoculation process. Miller and colleagues (2013), using the principles of psychological reactance, were able to use inoculation to elicit reactance against the source of the attack message, which lead to greater source derogation. Pfau and Kenski (1990), on the other hand, provided evidence that inoculation may be capable of protecting a message source i.e., the character of a political candidate.

Stone (1969), for the most part, did not find significant difference in the effect of inoculation messages based on gender. What he did find were females to be more influenced by the source of the message compared to males, a finding confirmed by Pfau and Kenski (1990).

Message Type

Over the years, inoculation researchers have tested different types of messages designed to maximize the inoculation’s effectiveness (Ivanov, 2012). For example, Banas and Miller (2013) successfully employed fact-based and logic-based inoculation messages. The fact-based inoculation treatments provided specific refutations of factual claims, while the logic-based messages refuted the reasoning process used in the counterarguments. Pfau and colleagues (2001), on the other hand, used cognitive, affective-happiness, and affective-anger messages to generate resistance. The cognitive messages used arguments, facts, and evidence. The affective-happiness and affective-anger messages relied on content that emphasized either how the desired goal would be facilitated by protecting the present attitude (affective-happiness messages) or how the goal attainment would be obstructed by the counter-attitudinal challenges and challengers (affective-anger messages). All of the different message types showed promise; however, Pfau and colleagues suggested that “resistance is optimized when the refutational preemption component of inoculation messages feature arguments supported by hard evidence in addition to the use of affect triggers which signal that goals may be thwarted” (2009, p. 93).

More recent research has also considered the role of psychological reactance in the message effectiveness. Szabo and Pfau (2001) discovered that inoculation messages can produce reactance, thus recent inoculation studies have added language and postscripts at the end of the inoculation message to ensure that receivers’ freedom of choice is not restricted by the message (e.g., Miller et al., 2013). Furthermore, Miller and colleagues structured the inoculation messages in a manner that elicited reactance against the counter-attitudinal challengers, thus increasing inoculation’s effectiveness (2013; also Niederdeppe, Heley, & Berry, 2015).


Although inoculation researchers have tinkered with the message content and structure, the effectiveness of the message has persisted (Ivanov, 2012). Its robust nature also crosses different communication modalities (e.g., Banas & Miller, 2013). To date, inoculation messages have been primarily presented in video (e.g., Nabi, 2003; Pfau, Van Bockern, & Kang, 1992) or print format (e.g., Ivanov et al., 2009b; Miller et al., 2013). Pfau and colleagues (2000) conducted a direct comparison of inoculation’s effectiveness presented in both modes and found the effects to be undifferentiated. Dillingham and Ivanov (in press) found similar results when manipulating the modality of the attack message. Inoculation was equally effective regardless of whether the attack was in a print or video format, thus illustrating the robustness of inoculation across different communication modalities.

Perhaps the greatest test of inoculation’s robustness was conducted by Banas and Miller (2013) who diluted the effects of the short print-based inoculation messages by using additional inoculation messages to forewarn participants of the effects of inoculation messages. In essence, they inoculate participants against the effects of inoculation, or metainoculation as termed by the authors. Subsequently, they presented participants with a 40-minute attack video supported by music, narration, and imagery in addition to the impressive length. Yet, inoculation messages still generated attitude protection, thus highlighting the robust nature of this message strategy.


The target outcomes of inoculation messages have varied and included established beliefs (e.g., McGuire, 1964), attitudes (e.g., Ivanov et al., 2009b), values (Bernard, Maio, & Olson, 2003), and behavioral intentions (e.g., Pfau et al., 2001). However, as previously discussed, inoculation has targeted a number of additional outcomes that play a role in the inoculation process such as self-efficacy, attitude accessibility, and attitude certainty, to name a few.

Overall, inoculation-elicited resistance is intricate and complex. Some processes are consistent, others complement (e.g., attitude certainty), and yet others compete (e.g., attitude accessibility) with McGuire’s originally identified process mechanisms: threat and counterarguing. Whereas inoculation research has increased our understanding of these processes, many questions and unknowns still remain. Throughout all of the research, one theme, however, has persisted. Inoculation works (see Banas & Rains, 2010). It is a robust strategy, which success has warranted application of inoculation in multiple contexts reviewed in the next section.

Contextual Application of Inoculation

As summarized in the introduction of this chapter, inoculation has been applied in numerous contexts, mostly with success. This section briefly addresses the most relevant contexts in which inoculation has been applied outside of health and risk and then proceeds to provide a more detailed account of inoculation’s success in the health and risk communication context. The reporting of different studies under specific contexts below is meant to be instructive rather than definitive. Numerous studies are cross-contextual, thus fitting well in multiple contexts.

Relevant Application Contexts Outside of Health and Risk Communication

Political Communication

One of the contexts that has benefited most from inoculation research is that of political communication. As Compton and Ivanov suggested, “[I]n some ways, political campaign practitioners were quicker to realize the potential of inoculation in political campaign settings than inoculation and political campaign scholars were” (2013, p. 256). As a political consultant, Jim Innocenzi has previously stated, “[I]noculation and pre-emption are what win campaigns” (as cited in Ehrenhalt, 1985, p. 2E). Practitioners’ experience and intuition were quickly followed by empirical support derived from controlled experimental designs. Pfau and Burgoon (1988) were the first to provide evidence that inoculation can blunt the impact of political attacks and their sources on voter intentions, as well as deflect the content of an attack. In general, inoculation has been shown to be an effective preemptive political campaign strategy when used to protect the candidate’s image and issue position (Pfau & Burgoon, 1988; Pfau et al., 1990) or when used to protect the position of a specific political issue (Pfau et al., 2006, 2008).

Commercial Communication

Marketing and advertising scholars were quick to realize the value of inoculation and systematically test its efficacy in the commercial communication context (Bither, Dolich, & Nell, 1971; Hunt, 1973; Sawyer, 1973; Szybillo & Heslin, 1973). As a result, inoculation has been demonstrated to be effective in protecting attitudes toward brands (Pfau, 1992) as well as countries as tourist (Ivanov et al., 2017) and manufacturing (Ivanov et al., 2009c) destinations from slippage. In addition, Compton and Pfau (2004) successfully incorporated inoculation as a resistance strategy against credit card marketing promotions aimed at college students. In a different study, Bechwati and Siegal (2005) were able to show that inoculation can aid the product prechoice process that results in lower product returns. In addition, inoculation scholars have proposed that inoculation may be able to protect buyers from experiencing post-purchase remorse (Ivanov, Parker, & Compton, 2011) and recommended inoculation as a viable strategy for protecting the positive images of celebrities and corporations (Ivanov & Parker, 2011).

Corporate Communication

Haigh and Pfau (2006) illustrated the positive impact inoculation can have on internal corporate communication. As their study’s results showed, inoculation may be an effective strategy in strengthening organizational identity, commitment, and organizational citizenship behaviors. On the other hand, Dillingham and Ivanov (in press) tested the efficacy of inoculation in an external corporate communicative setting. By focusing on the problem of unanticipated widespread sell-offs of securities motivated by a financial crisis, Dillingham and Ivanov were able to use inoculation strategy to fortify the “stay in the market” beliefs of individuals.

Public Relations

Burgoon, Pfau, and Birk (1995) believed that issue-advocacy campaigns used by organizations serve an inoculating function by protecting pro-organizational attitudes. Their findings supported this belief. Wan and Pfau (2004), on the other hand, successfully applied inoculation in the context of pre-crisis communication. More specifically, the authors were able to show that inoculation protected pro-organizational attitudes from slippage following an organizational crisis. Wigley and Pfau (2010) found similar results showing the ability of inoculation, used as a pre-crises treatment message strategy, to protect the reputation of an organization in the aftermath of a crisis.

Interpersonal Communication

Interpersonal communication is an understudied context in inoculation research, but one full of promise. For example, Sutton (2011) focused on interpersonal relationships and the ability of inoculation to combat the effects of improperly coping with jealousy. Inoculation did not augment the experience of jealousy, but it did improve the likelihood that individuals would use a positive jealousy expression strategy when encountering a jealousy provoking stimuli (Sutton, 2011).

Cross-Cultural Communication

Ivanov and colleagues (2012b) investigated the impact of culture on the effectiveness of the inoculation process. Their results were encouraging. Although culture moderated the process and effectiveness of inoculation, this strategy was still capable of protecting established attitudes even when implemented in a culture with values and message-processing patterns incongruent with the structure and content of the inoculation message.

Instructional/Educational Communication

One of the first ventures of inoculation in the area of instructional and educational communication context was rather unsuccessful. Compton and Pfau (2008) tested whether inoculation could protect students’ attitudes against pro-plagiarism arguments. While the results were disappointing, the potential for inoculation in this context remains to be significant as inoculation is perfectly positioned to aid the development of successful instructional and training messages and strategies (e.g., Kingsley Westerman, Margolis, & Kowalski-Trakofler, 2011).

Relevant Application Contexts in Health and Risk Communication

From a health and risk communication perspective, as previously suggested, inoculation may be used as a persuasive strategy of change/restoration (i.e., a curative function) or attitude/behavior formation (Ivanov et al., 2017; Wood, 2007). It may also simultaneously serve multiple functions, that is, curative and preventive (Ivanov et al., 2017). For example, regardless of the initial belief valence (i.e., supportive, neutral, or opposing), Ivanov and colleagues (2016) successfully used inoculation to enhance the general public belief about the ability of the U.S. government to prevent and minimize the effect of politically-motivated acts of violence. The inoculation treatment successfully withstood the presentation of a simulated attack on a U.S. airliner. In addition, inoculation was effective in generating a “blanket of protection” that extended over beliefs about the government’s ability to deal with national crises in general. Perhaps just as importantly, inoculation lowered the intensity of experienced fear elicited by the threat of violent attacks, as well as strengthened the perceived ability of individuals to cope with the outcome of a crisis. In a different study, irrespective of initial attitudinal valence, Blervacq (2010) was able to use inoculation to boost individual’s physical activity.

Yet, the preponderance of accumulated knowledge on inoculation’s effectiveness in the area of health and risk communication is focused on the preventive function of an inoculation message strategy designed to “enhance the resistance of healthy attitudes and behaviors in danger of slippage” (Ivanov, 2012, p. 77). Indeed, McGuire’s successful original testing of the theoretical mechanisms employed the protection of health-related beliefs such as regular dental hygiene as well as annual health checkups and tuberculosis screenings (McGuire, 1964). His original work has been subsequently extended to a number of other risk- and health-related beliefs, attitudes, and behaviors.

Smoking Prevention

The extant inoculation research has demonstrated the ability of inoculation to impact smoking initiation (Compton, 2013; Ivanov, 2012). For example, Pfau and colleagues (1992) discovered that inoculation may be able to protect at risk adolescents with low self-esteem from succumbing to the pressure to smoke with some effects lasting over 20 weeks (Pfau & Van Bockern, 1994). Banerjee and Greene (2006, 2007) discovered similar inoculative effects for adolescents participating in the researchers’ anti-smoking intervention workshops.


Duryea (1982, 1983), Duryea, Ransom, and English (1990) suggested that inoculation may be a successful strategy to employ in preventive alcohol education. As Godbold and Pfau (2000) discovered, inoculation messages with normative focus were able to provide more accurate estimations on the part of adolescents regarding how many of their peers were consuming alcohol, thus providing a firmer base aiding the ability to withstand pressures to consume alcohol. In a separate study, Parker and colleagues (2012) found indirect cross-protection effects on college students’ negative attitudes toward binge drinking. More specifically, in attempting to protect the positive attitudes toward condom use with inoculation, the researchers also discovered more pronounced negative attitudes toward binge-drinking, ostensibly as a result of the relatedness between these two risky behaviors (2012).

Unprotected Sex

As previously suggested, Parker and colleagues (2012) investigated the possibility of using inoculation as a strategy in protecting the attitudes of college students toward condom use. The results showed that inoculation messages led to greater level of experienced threat and greater production of counterarguments. In addition, inoculation contributed to more negative attitudes toward the counter-attitudinal attacks (or pressures) and more positive attitudes toward condom use.


In a recent study, Wong and Harrison (2014), and Wong (2016) investigated the efficacy of inoculation in protecting the positive attitudes toward HPV vaccination. Their results were encouraging. Not only did they discover inoculation messages targeting HPV vaccination to protect the attitudes toward HPV vaccination from challenges, but they also discovered that inoculation messages communicating the import of vaccination practices in general may also provide protection of pro-HPV vaccination beliefs against challenges. This finding is both theoretically and practically significant as it provides further evidence of the ability of inoculation to afford an umbrella (or blanket) protection over multiple attitudes within an issue domain.

Health-Related Policy

Besides showing efficacy in protecting specific risk and health-related attitudes and behavioral intentions, inoculation may have the ability to influence health-related policy as well. For example, in numerous studies (e.g., Miller et al., 2013; Pfau et al., 1997, 2005), inoculation has been shown to be effective in protecting attitudes in support of the government’s restriction of: gambling, TV violence, sale and distribution of hand guns, and legalization of marijuana.

In a recent study, Niederdeppe, Heley, and Barry (2015) tested the efficacy of inoculation in generating support for policies designed to reduce cigarette use, obesity, and painkiller addiction against the impact of industry anti-policy messages. The results were very encouraging as the inoculation messages were not only effective immediately after being delivered, but also outperformed narrative messages when the effect was assessed after a week. In general, inoculation may be an effective strategy that could assist health-related policy promotion.

Other Risk and Health-Related Topics

In addition to the above topics, inoculation may have the ability to protect other risk- and health-related attitudes, behaviors, or policies. For example, addiction intervention research is presently underway testing the efficacy of inoculation-based strategies in protecting recently sober individuals from relapsing. Another contemporary study is attempting to discover whether inoculation can guard against persuasive messages suggesting some erroneous positive outcomes of indoor bed tanning.

However, inoculation is not limited to the above topics. Matusitz and Breen have suggested that inoculation may be used as a strategy for preventing youth from joining gangs (Breen & Matusitz, 2008) or as a strategy for reducing recidivism in criminal prison inmates (Matusitz & Breen, 2013). Rosenberg (2004) argued that inoculation could be an effective strategy in preventing increased verbal aggression in schools. Additional promising areas for application of inoculation-based strategies may include the promotion and protection of healthy eating habits, as well as positive attitudes (and behaviors) toward mammograms, colonoscopies, breastfeeding, and regular exercise, just to name a few. As Ivanov suggested, the “application of the strategy [is] boundless” in the health and risk communication context (2012, p. 77).

Inoculation Message Design

Prior to discussing how to effectively design inoculation messages for application in the aforementioned contexts, two important message considerations warrant attention. First, inoculation messages are not immune to the dangers of inadvertently eliciting the process of psychological reactance (Ivanov, 2012). As mentioned earlier in this chapter, in a study testing the efficacy of inoculation antismoking messages, Szabo and Pfau (2001) demonstrated that inoculation messages, if not carefully constructed, can generate psychological reactance against the treatment message itself, which may have a counterproductive effect on the message’s effectiveness. A possible cue for how to combat this negative outcome comes from the message design template used by Miller and colleagues (2013) who purposely generated reactance targeting the attack, rather than the inoculation messages and messengers. To ensure that their treatment messages did not generate psychological reactance toward the inoculation message and source, the authors used a restoration postscript (see Miller et al., 2007) designed to restore the freedoms of the message receivers in making their own decisions on whether to adopt the messages or suggestions contained in the inoculation treatments.

Inoculation messages could also be used to preempt the occurrence of psychological reactance in pro-health persuasive messages. For example, Richards and Banas (2015) showed how campaigners may be able to inoculate individuals from the negative effect that psychological reactance has on the assimilation of message content promoting healthy behaviors. In their study, by combating the self-generated cognitions of individuals responsible for psychological reactance, inoculation messages were able to lower the intention of individuals to consume alcohol.

The second consideration is that of booster messages. Consistent with the medical (biological) analogy, the effectiveness of inoculation messages dissipates over time (Ivanov, 2012), whether as a result of message (Stiff & Mongeau, 2003) or motivation (Insko, 1967) decay. A medical remedy for this erosion of effectiveness is to use booster shots after a period of time from the initial inoculation. McGuire (1961) suggested that attitudinal inoculation messages may also benefit from booster shots. The results, however, are somewhat equivocal. Pfau and colleagues (2004) discovered that booster messages delivered approximately a week to three weeks after the treatment were able to sustain the process of counterarguing for more than six weeks. In a different study, boosters were applied 70 days after the presentation of the treatment message with minimal effectiveness (Pfau et al., 1992). Pfau suggested that the main factors contributing to the effectiveness of booster messages are proper timing (Pfau et al., 2004) and treatment-message consistency (Pfau, 1995). Pfau believed that the booster message should match the treatment message for it to be effective. The latter assumption was challenged by Compton and Pfau (2005) as well as Ivanov and colleagues (2009a) who suggested that other forms of boosters (e.g., weakened attacks, forewarnings, etc.) may prove to be more effective in sustaining the effectiveness of inoculation.

Discovering the proper timing in which to introduce boosters continues to draw scholarly interest. In a recent study, Ivanov and colleagues (2016) demonstrated that offering a booster two weeks after the presentation of a treatment message and four weeks in advance of the attack message did not produce appreciable boosting effect. Yet, following up the initial booster with a second one two weeks later did enhance the inoculation effect. What was not clear from the Ivanov et al. study is whether the boosted effect was a result of better timing or application of multiple boosters.

The study also tested the potential of attack messages to serve a boosting function by rendering the threat to the attitude real, a suggestion previously introduced by Ivanov and colleagues (2009a). The results showed that attack messages do not have boosting power, at least not in their full force. Ivanov and colleagues (2016), consistent with Compton and Pfau (2005), suggested that weakened attacks may better serve a boosting function. They also wondered whether booster messages in the form of forewarnings may be effective in extending the efficacy of inoculation messages.

The efficacy of boosters continues to intrigue and frustrate inoculation scholars. As Ivanov and Colleagues (2016) submitted, much more needs to be learned about the best way to structure and time booster messages. A new study testing different booster message forms, length, and timing is currently underway.

Contextual Considerations and Formative Research

Inoculation messages have to account for the contextual constraints faced in the environment in which they are applied. For example, the message-processing capabilities of the target audience have to be taken into consideration during the message design. As a result, the target audience’s reading grade level should not be exceeded in the message (e.g., Miller et al., 2013) and the modality used to disseminate the message should be considered. Younger audiences may be more receptive to video message delivery (e.g., Pfau et al., 1992) compared to college students who may be equally receptive to video and print (e.g., Pfau et al., 2000).

Research has also shown that the base of the attitude that target audiences hold may impact the effectiveness of the inoculation message (Ivanov et al., 2009b). According to the findings by Ivanov and colleagues, if the base of the held attitude is predominantly affective (e.g., I do not smoke because it is disgusting), as opposed to cognitive (e.g., I do not smoke because it is detrimental to my health), inoculation messages that feature affect-laden content matching—rather than mismatching—the inoculation treatment to the base of the attitude should generate greater resistance. The reverse is the case for attitudes with a predominantly cognitive base. However, Ivanov et al.’s (2012c) research findings demonstrated that in cases where the attitudinal challenges are repeated, inoculation messages featuring both affective and cognitive content may be just as effective as the matched attitude base/inoculation treatment combination, which, in turn, may alleviate the need to assess the base of the targeted attitude. Thus, in these situations, which should constitute the majority of occurrences, as seldom are attitudinal or behavioral challenges singular in nature, the design of inoculation messages should follow Pfau and colleagues’ recommendation of using “arguments supported by hard evidence in addition to the use of affect triggers which signal that goals may be thwarted,” (2009, p. 93).

Another important component in effective inoculation message design is conducting a sound formative research, which can inform the message designer of, among other things, the: primary attitudinal (or behavioral) challenges in need of refutation; base of the attitude; target audience characteristics, such as message processing capabilities, motivation, and modality preferences; source(s) of potential attitudinal (or behavioral) challenges; and context in which the challenges are likely to take place. In addition, before implementing an inoculation-based strategy, the inoculation messages should be thoroughly pretested and augmented, if necessary, based on the pre-test feedback and/or results.

Message Components and Design

The first component in the inoculation message is the explicit forewarning. To remind, explicit forewarning is not required in inoculation messages, as threat could be generated implicitly with the presentations of weakened opposing arguments in the refutational preemption component of the message (e.g., Ivanov et al., 2016). Studies using inoculation simultaneously as a resistance (e.g., preventive) and persuasive (e.g., curative) strategy may choose to omit the explicit forewarning for pragmatic reasons. For example, informing young adolescents that the negative attitudes toward smoking are likely to face challenges may seem like a good practice with adolescents who indeed have negative attitudes toward smoking; however, those who have positive attitudes toward smoking would not find the forewarning of such challenges, which are consistent with their present attitudes, to be very diagnostic or relevant. Nevertheless, Ivanov and colleagues (2017) found the use of explicit forwarding not to have an adverse effect on target audience members with opposing attitudes; thus, there does not seem to be a pertinent need to omit the explicit forwarding from the inoculation message when applied to audiences with diverse initial attitudes.

The explicit forewarning alerts the message recipients to the vulnerability of their current attitude or behavior. It informs the target audience members that challenges to the current attitudes or behaviors are not only possible, but likely. It instructs them that complacency can lead to undesirable attitudinal or behavioral change by telling the audience members that others like themselves have already yielded to these highly persuasive challenges. It then proceeds to provide support for this claim. Finally, it asks the target audience members whether they feel prepared to effectively defend their attitudes or behaviors by suggesting that others like themselves who felt prepared, did indeed succumb to the impending challenges. The following excerpt from the Parker et al. (2012) study designed to protect the positive beliefs toward condom use provides an example of explicit forewarning:

. . . recent research shows that there is more pressure than ever before for college students not to use condoms. This research proves that college students are often succumbing to the pressure not to use condoms; in fact, many young people like you who think they should use condoms are often persuaded by sexual partners not to use this form of protection . . . Are you prepared to resist these persuasive appeals potentially orchestrated and practiced by your current or future partners? How about resisting these appeals when coming from your friends or perhaps fraternity brothers or sisters? The results of current research show that you may not be as prepared to defend your beliefs as you may think you are.

As could be noticed from the above forewarning, multiple sources of potential challenges were identified, which was a direct result of formative research. In addition, no specific time or location in regard to when and where these challenges may occur were identified in the forewarning. The location and timing were left as more general because formative research indicated the challenges can occur at different locations, at different days of the week, and at different times of the day.

The second component of the inoculation message is the refutational preemption. This component of the message begins with a presentation of arguments on the opposite side of the issue, but presented in a weakened format. Traditionally, these arguments are presented as single sentences (e.g., Ivanov et al., 2012a) or paragraphs (e.g., Parker et al., 2012) and rely on anecdotes, testimonials, and/or dubious evidence grounded in questionable logic. The following is an excerpt from the Parker et al. (2012) aforementioned study:

One of the appeals used to persuade you to stop using condoms states that you are no more at risk for a sexually transmitted disease such as HIV . . .: “If we were at a high risk for contracting HIV, then how come this is not something that is made a big deal on college campuses . . . I don’t have HIV and I don’t use condoms during sex. Actually, none of my friends do and we are all fine . . . We are young, so we are at lower risk . . . So, as I said, you are not any better off wearing a condom.”

The questionable logic of the opposing argument is then refuted in the rebuttal using strong evidence, fact, and/or statistics designed to overwhelm the opposing claims as the following excerpt from the Parker et al. (2012) study illustrates:

This testimonial is as ignorant and dubious as it gets. The fact is young people in the United States are at persistent risk for HIV infection . . . According to the Centers for Disease Control and Prevention, since 1991, AIDS has been the sixth leading cause of death in the United States among 15- to 24-year-olds. In fact, half of all new HIV infections in the United States occur in people who are under 25 years old; thousands of college students acquire new HIV infections each year. Most new HIV cases in younger people are transmitted through unprotected sex . . . In fact, research published in the Sexually Transmitted Diseases journal shows that using a condom during intercourse to protect against HIV transmission is 10,000 times safer than not using a condom! . . .

The format of the refutational preemption component has traditionally incorporated the presentation and refutation of two (e.g., Ivanov et al., 2009b) to three (Parker et al., 2012) of the most relevant oppositional arguments, although there is currently no evidence to suggest what may be the most optimal number of refuted arguments. A research study systematically testing the efficacy of inoculation messages using different numbers of refuted arguments is currently underway.

The concluding paragraph of the inoculation message has traditionally included a final warning and a call to action as the following excerpt from the Parker et al. (2012) study illustrates:

When condoms are not used during every sexual intercourse, you risk transmitting a sexually transmitted disease and HIV/AIDS, which can permanently damage your life and seriously impede your goals, not to mention your health. Don’t risk your health or end up with a baby before you are ready; wear a condom every time you have sexual intercourse!

However, recent research has started to question this approach. As discussed earlier in this section, inoculation messages are not immune to creating psychological reactance. Using what may be perceived by the target audience as highly controlling or commanding language contained in the last sentence of the final paragraph accentuated by an exclamation mark, may potentially lead to undesirable message results i.e., the generation of reactance toward the inoculation message. Some of the most recent research has taken a different approach to concluding the inoculation message. Take for example the inoculation message ending in the Ivanov and colleagues (2016) study, which focused on strengthening and protecting the beliefs in government agencies’ ability to prevent and/or minimize the effect of terrorist attacks. The call to action in their study is still present, but more autonomy is given to the message recipient to make up his or her own mind on the issue. Below is an excerpt from the referenced study:

So, as you reflect on your beliefs about DHS and our government’s ability to prevent and minimize the effects of terrorist attacks, please bear in mind the current success and relentless preparedness described here. No institutions in the world are better prepared for these challenges than DHS and our government. Of course, what you choose to believe is up to you; but at least now, you have an accurate understanding of the situation.

As can be seen above, there is no usage of an exclamation mark and the message receiver is reminded that he or she is free to choose what to believe. Thus, carefully structuring the call to action as to avoid generating reactance against the inoculation message itself may be a more effective way to conclude the inoculation message and ensure its efficacy.

Limitations of Inoculation-Based Strategies

Inoculation is by no means a perfect strategy. As with most strategies, it has drawbacks that should be considered. Some of these drawbacks are perceptual (e.g., the danger of making counterarguments salient), while other are indeed substantive (e.g., the ability of inoculation to generate reactance, the impact of metainoculation, and the relatively small effect sizes). This section will note some of these concerns.

Danger or Making Counterarguments Salient

A common concern with using inoculation messages is rooted in their two-sided nature. Inoculation messages provide opposing arguments, thus making the very existence of these counterarguments salient to message receivers. As a result, practitioners may fear that the introduction of counterarguments may destabilize the attitude in absence of an attack, by highlighting its vulnerability (see Dillingham & Ivanov, in press). However, recent studies have shown that inoculation does not produce attitudinal harm in the absence of an attack (Dillingham & Ivanov, in press; Ivanov et al., 2017; Wigley & Pfau, 2010). Instead, studies have found inoculation messages to have a strengthening attitudinal effect in the absence of an attack, rather than compromising the attitude (Ivanov et al., 2017; Wigley & Pfau, 2010). Thus, the danger of making counterarguments salient to message receivers does not seem to present a major strategic concern.

Ability of Inoculation to Generate Reactance

Inoculation messages are capable of generating psychological reactance (Brehm, 1966) that can obstruct, rather than facilitate, inoculation message acceptance. As previous research has shown (Szabo & Pfau, 2001), if not designed with care and accounting for the potential threat of eliciting reactance, inoculation messages are indeed capable of generating unintended reactance against the inoculation message itself. Thus, it is imperative that inoculation messages are designed using language that does not restrict the perceived freedoms of message receivers to self-determine. As the example in this chapter demonstrates, this can be accomplished by avoiding the use of controlling language, embedding restoration postscripts at the end of the message, and pre-testing the messages (see Ivanov et al., 2016; Miller et al., 2013).

On the other hand, as aforementioned, inoculation could be used strategically to effectively elicit reactance targeted at the attacking source and/or message and thus enhance resistance to attitudinal pressures (Miller et al., 2013). In addition, inoculation could be used to preempt the experience of message reactance and thus facilitate persuasion, or message acceptance, in situations when persuasion, rather than resistance, is the goal (Richards & Banas, 2015).

Inoculation messages are capable of creating reactance that can thwart, rather than facilitate, the intended communication goal. However, careful message design can avoid the negative effect of undesired elicitation of psychological reactance. In addition, inoculation can also be used to exploit the positive outcomes of psychological reactance.

The Impact of Metainoculation

In a very innovative study, Banas and Miller (2013) introduced an antidote to inoculation in the form of metainoculation. In their study, the authors preempted the preemptive strategy of inoculation by cuing individuals to the purpose of inoculation messages and how they work in an effort to prepare these individuals to counter the effects of inoculation. The metainoculation strategy worked, as it lessened the effect of the subsequent inoculation messages, thus helping facilitate, rather than reduce, persuasion.

Consequently, metainoculation can inhibit the full effect of inoculation messages. However, the authors also noted that although the inoculation effect was compromised by the metainoculation message that preceded the presentation of the inoculation message, the effect was not nullified. The results indicated that inoculated individuals who were pretreated with a metainoculation message were more resistant to conspiracy theory propaganda messages compared to individuals who received neither the metainoculation nor the inoculation messages.

As a result of the above, two important takeaway points need to be stated. First, although the inoculation’s effectiveness may be diluted, its effect does not appear to be eliminated by metainoculation. Thus, inoculation messages could be successful even in situations when preempted by metainoculation. Second, Banas and Miller (2013) attributed the success of metainoculation to heuristic processing. The authors used loaded terms to prime individuals by suggesting that they should avoid being manipulated like “sheep” by the inoculation messages and instead, should be “independent thinker[s]” who should make “up their own mind[s]” (Banas & Miller, 2013, p. 199). As a result, metainoculation seems to produce similar outcomes as psychological reactance. More specifically, with metainoculation, message receivers may perceive the freedoms to make up their own minds as being restricted by the inoculation message. As such, using the same aforementioned strategies to combat psychological reactance may help facilitate resistance and blunt the effect of metainoculation.

Relatively Small Effect Sizes

The effect sizes of inoculation messages could be classified as small. More specifically, Banas and Rains’s (2010) meta-analysis produced a mean effect size of d = .43. According to Cohen (1988), this would be a small magnitude effect, with moderate effects starting at d = .50. Hence, the small inoculation effect sizes could generate hesitance on the part of risk and health message strategists in regards to using this strategy. However, Banas and Rains suggest that the effect sizes of inoculation messages should be considered in context (2010). As these authors explain, in health campaigns aimed at increasing young adults’ resistance from engaging in unhealthy behaviors, even small increases in likelihood of resisting the risky persuasive appeals are of “great value” (Banas & Rains, 2010, p. 302).

As mentioned in this chapter, an ongoing inoculation-based intervention study is presently exploring the efficacy of the strategy in protecting recently sober addicts living in a recovery home from experiencing relapse. Prior to honoring the recovery home’s request to perform the inoculation-based intervention, the researchers, in the spirit of full disclosure, forewarned the home’s management that any positive effects experienced were likely to be modest. The response from the home’s management was instructive and poignant, as it suggested that even if one person was saved, the strategy would have been a success and well-worth the effort and investment, thus reiterating Pfau and colleagues’ assertion that in “the context of resistance research . . . small effect sizes are common and are meaningful” (Pfau, Haigh, Sims, & Wigley, 2007, p. 212, emphasis in original).

Conclusion and the Future of Inoculation Research

More than ten years have passed since Compton and Pfau declared that inoculation is a theory “at maturity” (2005, p. 97), thus leading Miller and colleagues to suggest that:

. . . we may be tempted to conclude the theoretical basis of inoculation is settled, its contribution to resistance research exhausted, and its potential for further development minimal. On the contrary, Compton and Pfau (2005) have noted that while some may dismiss inoculation as ‘‘antiquated theory,’’ it continues to grow in its theoretical development and application, and it is by no means ready for retirement.

(2013, pp. 127–128)

Indeed, according to Miller and colleagues, inoculation has emerged as the “most consistent and reliable method for conferring resistance to persuasion” over the past 50 years (2013, p. 126). As this chapter illustrated, inoculation theory is heavily informed by our understanding of the principles of social influence, persuasion, and message processing, which provide the basis for understanding the inoculation-elicited process of resistance. For example, the mechanisms of inoculation are very consistent with the predictions of the elaboration likelihood model (ELM; Petty & Cacioppo, 1986). In accordance with the ELM, inoculation generates biased message processing as the explicit forewarning, and issue importance (i.e., issue involvement) motivates individuals to engage in anticipatory counterarguing i.e., accumulate information and arguments that help support their message position as well as help counterargue opposing views (Petty & Cacioppo, 1986). Thus, not surprisingly, inoculation researchers are consistently introducing different theories and theoretical concepts in their testing of the inoculation mechanisms with the goal of not only better understanding the inoculation process of resistance, but informing more effective message design. In addition to this research being theoretically rewarding, the real pragmatic value rests in the application of these advancements in numerous contexts such as those exemplified in this chapter.

As Compton and Pfau have suggested, inoculation “theory continues to inform cutting-edge and exciting scholarship, adding nuance to our understanding of persuasion theory and offering practical applications” (2005, p. 136). Indeed, current research continues to apply the theory in new contexts by testing and retesting its logic and pushing the theoretical boundaries in new and exciting areas such as cross-protection, post-inoculation talk (PIT), and two-sided message persuasion. This groundbreaking research has shown inoculation to be a more robust strategy than McGuire ever imagined. Putting all of the advancements together, we are discovering that, via social diffusion (PIT), an inoculation message may spread its influence far beyond the reach of the specific medium disseminating the message while concomitantly protecting not only the target attitude or behavior, but related ones as well; doing so irrespective of the target’s attitudinal valance at the transmission of the inoculation message.

The future of inoculation scholarship is bright and inspiring. Its theoretical advancement and contextual application perhaps is only limited by our imagination. The vigorous research that has underlined the vibrancy of the theory over the years, and especially in recent history, will only serve to secure its place as the most vital theory of resistance to influence.

Further Reading

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