How Should Doctors Frame the Risk of a Vaccine’s Adverse Side Effects? It Depends on How Trustworthy They Are

Background How health workers frame their communication about vaccines’ probability of adverse side effects could play an important role in people’s intentions to be vaccinated (e.g., positive frame: side effects are unlikely v. negative frame: there is a chance of side effects). Based on the pragmatic account of framing as implicit advice, we expected that participants would report greater vaccination intentions when a trustworthy physician framed the risks positively (v. negatively), but we expected this effect would be reduced or reversed when the physician was untrustworthy. Design In 4 online experiments ( n = 191, snowball sampling and n = 453, 451, and 464 UK residents via Prolific; M age ≈ 34 y, 70% women, 84% White British), we manipulated the trustworthiness of a physician and how they framed the risk of adverse side effects in a scenario (i.e., a chance v. unlikely adverse side effects). Participants reported their vaccination intention, their level of distrust in health care systems, and COVID-19 conspiracy beliefs. Results Physicians who were trustworthy (v. untrustworthy) consistently led to an increase in vaccination intention, but the way they described adverse side effects mattered too. A positive framing of the risks given by a trustworthy physician consistently led to increased vaccination intention relative to a negative framing, but framing had no effect or the opposite effect when given by an untrustworthy physician. The exception to this trend occurred in unvaccinated individuals in experiment 3, following serious concerns about one of the COVID vaccines. In that study, unvaccinated participants responded more favorably to the negative framing of the trustworthy physician. Conclusions Trusted sources should use positive framing to foster vaccination acceptance. However, in a situation of heightened fears, a negative framing—attracting more attention to the risks—might be more effective. Highlights How health workers frame their communication about a vaccine’s probability of adverse side effects plays an important role in people’s intentions to be vaccinated. In 4 experiments, we manipulated the trustworthiness of a physician and how the physician framed the risk of adverse side effects of a COVID vaccine. Positive framing given by a trustworthy physician promoted vaccination intention but had null effect or did backfire when given by an untrustworthy physician. The effect occurred over and above participants’ attitude toward the health care system, risk perceptions, and beliefs in COVID misinformation.