The Centers for Disease Control and Prevention (CDC) made a big revision to its website last year, at the behest of Robert F. Kennedy Jr., the secretary of the Department of Health and Human Services and a longtime anti-vaccine advocate.

The website now states that a link between autism spectrum disorder and vaccinations is possible and should be studied—even though such a link has been disproved by a large body of research.

US childhood immunization rates continue to decline, and the CDC is the foremost public health authority in the United States. This revision dismayed public health and medical experts, who warned that even more parents might delay or skip lifesaving vaccines.

It seems those concerns were valid. A study published today in the journal Science shows that the revised CDC messaging could discourage people from vaccinations. 

Kennedy’s revision makes people think vaccines are less safe 

Researchers surveyed 2,989 adults living in the United States, who were separated into three groups. 

The first group of participants read the earlier version of the CDC website, which clearly stated the scientific consensus that there’s no link between vaccination and autism. 

A second group read the Kennedy version, which states, “Studies have not ruled out the possibility that infant vaccines contribute to the development of autism,” and, “Studies supporting a link have been ignored by health authorities.”

A third group received neither statement, acting as a control.

Using a seven-point scale, participants were asked whether they agreed or disagreed with certain statements about vaccines, and about their trust in science and government.

Those who read the CDC revision judged vaccines to be riskier, compared with those who hadn’t read the updated website. Perhaps unsurprisingly, this group was less likely to get recommended vaccinations.

The second group was also less likely to trust the CDC and were more likely to engage in conspiracy-based reasoning. Notably, the study found that the revised CDC statement had a similar effect on respondents regardless of their political affiliation.

Science messaging should be clear, transparent

The findings show that public trust and people’s health decisions can be shaped by messages from official government websites, said lead author Robert Böhm, PhD, a social psychologist at the University of Vienna.

“That means [messaging] should be held to a very high standard—not unlike scientific findings themselves,” said Böhm.

Adam Berinsky, PhD, a political scientist and director of Massachusetts Institute of Technology (MIT) Political Experiments Research Lab, agreed that the study demonstrates the importance of government communication. 

We can see directly that faith and trust in vaccines can be either increased or decreased by the way the message is framed.

Berinsky, who did not contribute to the research, noted that most people don’t pay close attention to health guidelines, making government entities like the CDC an authoritative voice.

“We can see directly that faith and trust in vaccines can be either increased or decreased by the way the message is framed,” he said.

Böhm suggests there should be clear rules for how such information is reviewed and peer-checked before it is published on government websites like the CDC’s. In the future, he’d like to study whether misinformation about vaccines and autism in one country can spill over to influence people in other countries.