White evangelical Christians have resisted getting vaccinated against COVID-19 at higher rates than other religious groups in the United States. A new study by Yale researchers provides evidence that persuading these vaccine holdouts to get their shots has only gotten more difficult.

The study, published in the journal Proceedings of the National Academy of Sciences, combines two survey experiments testing the effectiveness of various persuasive messages in shifting white evangelicals' attitudes about vaccination. The first survey was conducted in October 2020, while Donald Trump was president and before the COVID-19 vaccines were approved for use in the United States, and the second occurred in May 2021, several months after people started getting jabs.

In the first survey, a message appealing to people's sense of community interest, reciprocity, and the potential embarrassment of getting others sick after refusing the vaccines proved most effective in persuading white evangelicals to embrace vaccination. The second survey showed that these messages, as well as others, were no longer effective in May 2021 in changing unvaccinated white evangelicals' views on the vaccines.

At this point, unvaccinated white evangelicals seem resistant to messaging aimed at persuading them of the benefits of being vaccinated against COVID-19. It's not clear whether this is because resistance to vaccination among white evangelicals has increased over time or that the current holdouts were always the least persuadable. What is clear is that messaging that was effective last fall, before vaccines were approved, now seems ineffective."

Gregory A. Huber, the Forst Family Professor of Political Science in Yale's Faculty of Arts and Sciences, and co-author of the study

Scholars and faculty from Yale's School of Medicine, School of Public Health, School of Nursing, Institution for Social and Policy Studies, Department of Political Science, and the Institute for Global Health collaborated on the study with support from Yale's Tobin Center for Economic Policy.

The initial survey, fielded on a nationally representative sample of 855 white evangelicals, gauged how various messages affected white evangelicals' intentions to get vaccinated, their willingness to advise a friend to get the shots, and their judgments of people who refuse the vaccine. Respondents were randomly assigned to one of seven conditions: a placebo message unrelated to COVID-19, a baseline message about vaccine efficacy, or five treatment messages that added specific content to that baseline.

The treatment messages included an appeal to people's community interest, emphasizing that vaccination protects others, who would in turn reciprocate that protection by getting vaccinated themselves. Another added language to the community interest message which evoked the embarrassment one would feel if they didn't get vaccinated and infected somebody.

Three other messages were values based: One asserted that refusing the vaccine is reckless, not brave, and emphasized that getting vaccinated to protect others demonstrates real bravery; the second appealed to people's sense of freedom by arguing that vaccination would end restrictions intended to contain COVID-19; and the third values-based message suggested that not getting vaccinated makes someone seem like they don't understand science.

Overall, the message appealing to community interest, reciprocity, and a sense of embarrassment was the most persuasive, increasing all three outcomes relative to the placebo message: A 30% increase in intention to vaccinate, a 24% increase in willingness to advise a friend to get vaccinated, and a 38% increase in negative opinions of people who decline the vaccines.

However, the same message proved ineffective in the second survey, which was performed on a nationally representative sample of 2,419 unvaccinated white evangelicals. The message appealing to community interest and reciprocity also failed to persuade respondents, as did three revised values-based messages: one emphasizing former President Trump's role in getting the vaccines developed; another stressing the point that vaccination would eliminate the need for government-mandated restrictions on personal freedom; and a third noting that people trust their doctors and that doctors support vaccination.

Neither survey showed that values-based messaging was successful at persuading white evangelicals to get vaccinated, contrasting with prior research that has found that values-consistent messaging increased positive attitudes towards masking among members of the same group.

"This study highlights the importance of testing and re-testing messages as the people requiring persuasion changes over time," said Scott E. Bokemper, an associate research scientist at Yale's Institution for Social and Policy Studies and the Center for American Politics, and co-author of the study. "It also demonstrates the difficulty in drawing broad conclusions from studies of population groups, even well-defined groups like white evangelical Christians, performed during a single point in time during the pandemic."