How Americans view science and scientists is strongly associated with whether they think vaccines are safe and effective — and helps explain partisan differences in perceptions of some vaccines, according to a new study led by a team from the Annenberg Public Policy Center (APPC) of the University of Pennsylvania.
Researchers found that Democrats viewed the measles, mumps and rubella (MMR), flu, and Covid-19 vaccines as safer and more effective than Republicans did. But when the researchers accounted for respondents’ broader perceptions of science and scientists, the partisan differences for the MMR and flu vaccines were no longer statistically significant.
That wasn’t the case with Covid-19. Even after accounting for perceptions of science, political affiliation remained significantly associated with how people viewed the Covid-19 vaccine, highlighting the extent to which it has become politicized.
“The Covid-19 vaccine really stands apart,” said lead author Dror Walter, an associate professor of communication at Georgia State University and an APPC distinguished research fellow. “With MMR and flu, views of science and scientists largely explain the partisan gap in perceptions of vaccines. With Covid-19 they don’t. Something beyond how people see science and scientists is shaping how Democrats and Republicans judge that vaccine.”
The study, published in October in the American Journal of Public Health, was conducted by a team that also includes Yotam Ophir, an associate professor of communication at the University at Buffalo, State University of New York, and an APPC distinguished research fellow; Patrick E. Jamieson, director of APPC’s Annenberg Health and Risk Communication Institute; and Kathleen Hall Jamieson, director emerita of APPC.
MMR vaccine seen as both safest and most effective
The researchers analyzed survey data collected in November 2024 from the Annenberg Science and Public Health (ASAPH) survey, with a national probability sample of 1,763 empaneled U.S. adults. Respondents rated the safety and effectiveness of the MMR, flu, and Covid-19 vaccines and answered questions about their perceptions of science and scientists.
The MMR vaccine was considered both the safest and the most effective of the three. On a four-point scale, it received an average safety rating of 3.54 and effectiveness rating of 3.63. The flu vaccine averaged 3.41 for safety and 3.03 for effectiveness.
The Covid-19 vaccine ranked lowest on both measures, with an average rating of 2.98 for safety and 2.81 for effectiveness.
The researchers say the differences may reflect the vaccines’ different histories. The MMR vaccine has been widely used for decades, while the Covid-19 vaccine was introduced amid an intensely polarized pandemic and became the subject of attacks by political figures and partisan media. The effectiveness of the seasonal flu vaccine, meanwhile, varies seasonally, depending in part on how well the vaccine matches circulating strains.
The perceived benefits of science stand out
Rather than simply asking whether people “trust science,” the researchers examined five aspects of how people view science and scientists, using the FASS (Factors Assessing Science’s Self-Presentation) model, originally introduced by APPC researchers in 2023: whether they consider scientists credible, prudent, and unbiased, and whether they consider science beneficial and self-correcting.
One factor stood out. Seeing science as beneficial was consistently associated with believing that all three vaccines were both safe and effective. Other perceptions — including scientists’ credibility, prudence, and lack of bias — were associated with some vaccine evaluations but not others.
Regarding the Covid-19 vaccine, the findings “suggest that positive perceptions of science and scientists were more strongly associated with vaccine perceptions among Republicans than among Democrats,” the researchers wrote.
“The use of FASS allows us to identify specific perceptions that could be used to guide science communication,” Ophir noted. “The results of this study, for example, suggest that when communicating about vaccines, in addition to highlighting their effectiveness and safety, we should also inform the public about the tangible benefits of science in general, and vaccines in particular for both individuals and societies.”
Implications for public health messaging
The findings come amid concern among public health experts about vaccine hesitancy and declining childhood vaccination rates. They also suggest that vaccine communication should not treat hesitancy as a single phenomenon: People may respond differently depending on the vaccine, its history, and the political environment surrounding it.
The results suggest that “science communicators should tailor messages based on the specific vaccine addressed, accounting for each vaccine’s history and perceptions of its safety and effectiveness, as well as the political affiliation of the target audience,” the researchers write.
For the Covid-19 vaccine in particular, the researchers suggest that communications may need to address concerns about scientific bias. Messages could explain the mechanisms science uses to identify and correct for bias, although the authors emphasize that future research is needed to test whether such approaches are effective.
The study also underscores the potential role of political leaders and the media in shaping perceptions of vaccines. The authors say responsible public communication consistent with the scientific evidence is particularly important when vaccines become politically polarized.
The study, “The Relationship Between Political Affiliation, Perceptions of Science and Scientists, and Perceived Safety and Effectiveness of the MMR, Flu, and Covid-19 Vaccines: United States, 2024,” was published online on Oct. 7, 2026, in the American Journal of Public Health. DOI: 10.2105/AJPH.2026.308606.
The Annenberg Public Policy Center was established in 1993 to educate the public and policy makers about communication’s role in advancing public understanding of political, science, and health issues at the local, state, and federal levels.
