Can endorsement by religious leaders move the needle on vaccine hesitancy?

Existing research, including work specific to COVID-19, suggests that endorsement by medical practitioners increases vaccine uptake. Yet, vaccine hesitancy persists despite health professionals continuing to widely endorse multiple vaccines to combat COVID-19 since late 2020. Could endorsement by other trusted leaders reduce vaccine hesitancy? Although some studies suggest that trust in religious leaders can influence individuals' health attitudes and behaviors, the evidence is mixed. Our study explores the potential added value of messaging by religious leaders across religious traditions - specifically, it asks whether their endorsement of the COVID-19 vaccine might increase vaccine uptake in an environment where health professionals are already endorsing vaccines. To investigate this question, we conducted an online survey experiment with 6,000 respondents across five countries with different dominant religions (Buddhism, Christianity, and Islam). Respondents were randomly assigned to either a control group that only included endorsement by medical practitioners or a treatment group that added either endorsement by religious leaders or, for comparative purposes, endorsement by political leaders. We found that endorsement by religious leaders reduced vaccine hesitancy only in one country. These findings corroborate existing research that medical practitioners are the best line of defense to combat vaccine hesitancy. They also suggest the limitations of endorsement by non-experts.