The Boomerang Effect of Vaccine Messaging

In public health, words matter. Describing people who hesitate about vaccines as “misinformed” is not the same as calling them “anti-scientific” or “socially dangerous.” And the difference is not merely rhetorical: it can affect people’s willingness to vaccinate.

A Study on Institutional Communication

This is the main conclusion of a study we conducted together with Diana Paraggio, which investigates how institutional communication shapes attitudes toward vaccination. The paper focuses on the Human Papilloma Virus (HPV) vaccine, used to prevent cervical cancer, and asks a question of direct relevance for health policy: can communication designed to fight vaccine hesitancy unintentionally make it worse?

The answer, according to the study, is yes.

The Experiment on the HPV Vaccine

We conducted a survey experiment with 150 women in a public maternal health facility in the province of Salerno, in Southern Italy. Participants were randomly exposed to one of three messages about parents who do not vaccinate their daughters against HPV. In the first message, these parents were described as simply “misinformed,” and the proposed solution was better information. In the second, they were portrayed as “anti-scientific,” with compulsory vaccination presented as the appropriate response. In the third, they were described as “socially dangerous,” with both compulsory vaccination and sanctions proposed as the solution.

These frames were not invented in the abstract. They were derived from an analysis of press statements released by the Italian Minister of Health between 2015 and 2017, a period marked by heated public debate over childhood vaccination and the reintroduction of stricter vaccine mandates in Italy. The study therefore examines not only whether people support vaccination, but also how they respond to different institutional narratives about those who hesitate.

The Study’s Findings

The results are striking. Compared with the group exposed to the “misinformed” frame, respondents exposed to the two more judgmental frames showed higher levels of vaccine hesitancy. Women exposed to messages portraying those who do not vaccinate their children as “anti-scientific” or “anti-social” are less willing to vaccinate their own children by more than 20% compared to those who were exposed a more neutral message (“misinformed”).

The study does not suggest that information about vaccines is irrelevant. On the contrary, among respondents favorable to vaccination, prevention emerged as the most frequent reason for supporting the HPV vaccine. Many saw vaccination as a fundamental tool to protect both individual and collective health. But among respondents who expressed hesitation, the motivations were more diverse: lack of information, concerns about vaccine safety, distrust of institutions and scientific authorities, and the belief that vaccination should remain a matter of personal choice.

Implications for Public Health

This is where communication can become counterproductive. A message intended to defend science and promote vaccination may be perceived by some audiences as moral condemnation or institutional coercion. Rather than building trust, it may reinforce resistance. In other words, the same message that appears strong and clear to policymakers may be experienced by some citizens as stigmatizing or threatening.

For public authorities, the implication is important. Communicating about vaccines is not only a matter of correcting misinformation or repeating scientific evidence. It also requires understanding how different audiences respond to blame, authority and coercion. In polarized contexts, messages that stigmatize hesitant individuals may strengthen the convictions of those already in favor of vaccination, but push others further away.

The broader lesson goes beyond HPV vaccination. Public health communication should be treated as a policy instrument in its own right. Like any policy instrument, it can produce intended effects — but also unintended consequences. When the goal is to increase trust in vaccines, the language used to promote them may be as important as the evidence behind them.