A new study published in Science has raised concerns that recent changes in U.S. federal vaccine messaging may be influencing public trust and increasing doubts about vaccine safety, despite the absence of new scientific evidence supporting such concerns.
Under President Donald Trump’s second term, the U.S. Centers for Disease Control and Prevention (CDC) revised its public guidance on vaccines and autism. The agency’s earlier position stated clearly that research had found no connection between vaccination and autism spectrum disorder. However, updated language introduced after November 2025 suggested that studies had not definitively ruled out a link and implied that some evidence supporting a connection had been overlooked.
That shift aligns closely with views long promoted by Health and Human Services Secretary Robert F. Kennedy Jr., a known vaccine critic, though the claim contradicts the broader scientific consensus.
Researchers led by Robert Böhm, a professor of psychology at the University of Vienna, examined how such messaging influences public perception. The study surveyed nearly 3,000 adults in the United States, exposing participants to either the CDC’s earlier guidance, the revised statement, or no statement at all before asking questions about vaccine safety, trust in health authorities, and willingness to vaccinate.
Results showed that exposure to the revised CDC messaging slightly increased concerns about vaccine risks and reduced willingness to receive recommended immunisations. In contrast, participants who read the earlier CDC guidance were more likely to trust vaccines and the public health system.
Trust in the CDC itself also shifted depending on which statement participants read, with confidence rising after exposure to the older guidance and declining after exposure to the newer version.
The research further explored common arguments used in anti-vaccine discourse, including demands for absolute scientific certainty, selective use of studies, and conspiracy-based claims. Participants exposed to the revised CDC messaging were more likely to accept these arguments as credible.
Böhm warned that while multiple factors influence vaccination behaviour, changes in official communication could contribute to weakening public confidence. He noted that even small declines in trust can have broader public health consequences, particularly for highly contagious diseases such as measles.
Separate research published in the journal Vaccine also points to the role of media consumption in shaping vaccine attitudes. Individuals who rely on certain right-leaning or alternative news sources were found to be significantly more likely to express vaccine hesitancy compared with those who follow mainstream outlets.
Experts say the findings highlight the importance of consistent public health messaging. According to Böhm, clear communication of scientific consensus has historically helped reinforce trust in vaccines, while conflicting or uncertain messaging risks undermining that trust.
Health researchers warn that if confidence continues to decline, even gradually, it could create vulnerable population clusters where preventable diseases may re-emerge.
