New Stanford Study Shows Promotion of COVID-19 Vaccines by Leading Republicans Can Influence Vaccine Intentions Among Supporters

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Endorsements of the vaccine by former President Donald Trump and other prominent Republicans boosted vaccine intentions among unvaccinated Republicans

PALO ALTO, Calif., August 06, 2021--(BUSINESS WIRE)--Ending the COVID-19 pandemic will require most Americans to be vaccinated. Yet vaccination has become politically polarized, with Republicans being the most consistently hesitant, and the gap in vaccination rates between U.S. counties that voted for Joe Biden and those that voted for Donald Trump continuing to grow.

As the Delta variant and latest surge in cases add urgency to outreach efforts, a new study by leading scholars from Stanford University, Columbia, Northwestern, and the Massachusetts Institute of Technology (MIT) shows that Republican elite encouragement of vaccines can significantly influence the vaccine intentions of Republican party supporters.

"While the proportion of Americans who report intending to get vaccinated, or who have already gotten vaccinated, has risen overall, Republicans continue to exhibit high levels of vaccine hesitancy," said Robb Willer, Professor of Sociology and Psychology at Stanford. "Therefore, effectively motivating Republicans to vaccinate is critical for containing the pandemic."

Elite Cues Shape the Attitudes of Partisans

Unvaccinated Republicans who were presented with the Republican elite endorsements reported 7.0% higher vaccination intentions than those who viewed the Democratic elite endorsement and 5.7% higher than those in the neutral control condition. Moreover, the study found that participants presented with endorsements from Republican leaders were more likely to report that they thought Trump and other Republicans would want them to get vaccinated, thereby influencing their vaccine intentions. On the other hand, vaccinated and unvaccinated Republicans who viewed pro-vaccine content from Democratic leaders expressed more negative attitudes toward the vaccine and reported being less willing to recommend vaccination to family and friends.

These results demonstrate the relative advantage of cues from Republican elites—and the risks of messaging from Democrats currently in power—for promoting vaccination among the largest vaccine-hesitant subgroup in the United States. They also offer key counter-evidence to the much publicized focus group data shared in March 2021 suggesting that vaccine-hesitant Republicans would be unlikely to heed vaccine recommendations from Republican leaders.

"Many prominent Republicans, including former President Donald Trump, have endorsed the vaccine. Our research suggests that publicizing these existing vaccine endorsements could make a huge difference," said co-author Sophia Pink of the Stanford Polarization and Social Change Lab. "The country cannot contain the virus without higher vaccination rates among Republicans. If Republican leaders take up vaccine promotion efforts with greater enthusiasm, there’s good reason to believe that their supporters will listen."

Methods and Additional Findings

Funded by the Stanford Center on Philanthropy and Civil Society, the study recruited a sample of vaccinated and unvaccinated Republicans and randomly assigned them to one of three groups. One group viewed a brief video of Trump encouraging vaccination, and read a short essay sharing vaccine endorsements from Trump and other prominent Republicans and commending Republicans’ contributions to vaccine development and distribution. Another group viewed a short pro-vaccine video featuring Joe Biden and read an essay with endorsements from Democratic leaders and supporters. A third group watched and read content on a neutral topic.

Among unvaccinated participants, results showed that the Republicans endorse condition increased vaccination intentions, when compared to the Democrats endorse condition and the neutral control. Additional measures showed evidence of backlash effects against Democratic leaders, as vaccinated and unvaccinated respondents in the Democrats endorse condition were less likely to recommend vaccination to friends and family, and expressed more negative attitudes toward the vaccine.

The study’s findings have three important implications. First, research in political science has established how elite cues shape the attitudes of partisans in the mass public. These study results show this dynamic can be applied to improve vaccination intentions among Republicans, as Willer and MIT Professor David G. Rand argued in a recent op-ed in The Washington Post. Second, these results extend prior research on the role of trusted sources in encouraging health behaviors, making them relevant for effectively intervening in other countries in which vaccine intentions are politically polarized. Third, the study clarifies the mechanisms driving partisan gaps in vaccination observed in current public health data, namely that lower willingness to receive the vaccine among Republicans is not only driven by misinformation about the vaccine but also by low awareness of Republican elite cues.

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Robb Willer, Sociology: (607) 339-6466,, @RobbWiller

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