Message Effectiveness of Fear Appeals in Vaccination Communication Campaigns: A Systematic Review

"[T]he current review contributes to the ability of medical and public health professionals to promote vaccination and to researchers' understanding of the efficacy of fear appeals in motivating attitudinal and behavioral responses related to vaccination communications."

To encourage vaccinations, health communication campaigns, such as posters, social media posts, public service announcements, and pamphlets, often use emotional appeals in addition to rational appeals. For example, fear appeals attempt to motivate receivers to reduce the communicated threat by adopting the recommended change in attitude, intention, or behaviour. This systematic review is designed to help public health officials, researchers, and healthcare professionals better comprehend the effects of fear appeals in vaccine promotional campaigns on message processing, persuasion, vaccination attitudes, and vaccination intentions.

This review included 54 cross-disciplinary quantitative empirical studies published in peer-reviewed journals and written in English. It included studies that examined the impact of fear appeals on various vaccination-related message outcomes, including information search and processing, word-of-mouth/advocacy, attitudes, and intentions. It included only causal studies (e.g., laboratory and field experiments); descriptive studies, such as correlational surveys that simply measured perceptions (e.g., fear of vaccination/disease, severity, susceptibility), were excluded. Most of the included studies, which hailed from 13 countries, were published from 2021 to 2023. Thus, interest in this topic among researchers has increased sharply in recent years.

The vast majority of studies (59.26%, n = 32) used a theoretical perspective of framing, followed by the Extended Parallel Process Model (EPPM), Arousal Theory, Health Belief Model, Protection Motivation Theory, and Theory of Planned Behavior.

The review documents inconsistent findings across studies, which it attempts to clarify by considering differences in research designs, sample populations, and outcomes measured. In general, the researchers find that fear appeals increase risk perceptions, message involvement, and vaccination attitudes. For example, 13 studies (24%) examined the direct effect of fear appeals on vaccination-related attitudes. Of these, nine studies (69.23%) found statistically significant main effects. Two studies revealed a statistically significant positive influence of a loss-framed message on the perceived outcome efficacy (perceived benefits and costs of receiving a measles, mumps, and rubella (MMR) vaccination) and perceived net benefit (the ratio of perceived effectiveness to perceived side effects of a COVID-19 vaccine).

However, fear appeals have less influence on vaccination intentions, especially among female and general adult populations or populations from Western cultures. On the other hand, the effect of fear appeals on vaccination intentions is stronger among student populations and those from China (People's Republic of China and Hong Kong) and other non-Western cultures. One possible explanation for these results is the cultural orientation of collectivism versus individualism. East Asian cultures tend to value collectivism, which emphasises serving the interests of and sharing among the members of a larger group. On the other hand, Western cultures value individualism, which emphasises viewing the self as distinct from others, individual freedom and power, and personal success. Prior research in different contexts has found that the effectiveness of fear appeals can differ between collectivist and individualist cultures.

Twenty-two studies (38.89%) found moderating effects of various factors on the relationship between fear appeals and vaccination intentions. Five studies (9.26%) reported statistically significant interaction effects between fear appeals and perceived response efficacy or perceived benefits. Trust-related variables, such as trust in family physicians and trust in vaccine benefits, also moderated the impact of fear appeals on vaccination intentions.

Fear appeals also exhibited negative effects in some studies. Fear appeals reduced: communication quality perceptions, including perceptions of social media message effectiveness and shareability; the perceived threat of disease; vaccination risk perceptions, as well as the perceived need for and safety of the vaccine; vaccine attitudes; response efficacy; perceived social pressure to be vaccinated; and vaccine intentions.

Also, fear appeals are less persuasive when promoting COVID-19 vaccines and boosters than they are for other vaccines (e.g., MMR).

Only one study measured behaviour: Sato and Takasaki found no difference in tetanus vaccine uptake following exposure to a flipchart containing image and text information with or without a fear appeal. According to the systematic review's researchers, "It is unsurprising that fear appeals had a greater effect on upstream message outcomes, such as information processing and attitudes, than downstream message outcomes, such as vaccination intentions or vaccine uptake behavior....In general, changes in attitudes lead to less change in terms of intentions and behavior."

According to the researchers, future research should compare fear appeal effectiveness in messages across vaccines or when combined with other elements, such as the endorser or type of evidence provided. Finally, future studies should explore other methodological approaches and measure underexplored message outcomes, such as vaccine uptake behaviour, in more naturalistic settings.