New study: US health authority increases vaccination and scientific scepticism

The scientific consensus is clear: vaccinations are neither causally nor statistically linked to autism. However, the US health authority Centers for Disease Control and Prevention (CDC) changed its communication under Secretary of Health Robert F. Kennedy Jr. and instead emphasises that a connection cannot be ruled out. An international research team led by the University of Vienna and with the participation of the University of Erfurt and the University of Copenhagen has analysed the consequences of this change in presentation. The results clearly show that the CDC's message reduces the willingness of the US population to be vaccinated, undermines trust in health authorities and promotes sceptical attitudes towards science. The researchers call for careful and evidence-based communication from health authorities. The study has now been published in the journal Science, one of the world's leading multidisciplinary journals on scientific breakthroughs and policy developments.

Large-scale online study
Communication from health authorities can have a major impact on public opinion. In November 2025, under pressure from the Trump administration, the CDC changed statements on its website about vaccinations and autism, emphasising alleged uncertainties about the current state of research. The scientific consensus previously clearly communicated by the CDC that vaccinations are neither causally nor statistically linked to autism was thus strongly questioned. An international research team from Vienna, Erfurt, Hamburg and Copenhagen, led by psychologist Professor Dr Robert Böhm from the University of Vienna, has now investigated the consequences of this change in communication. Professor Dr Cornelia Betsch from the Institute for Planetary Health Behaviour at the University of Erfurt is also involved.

In an online study with 2,989 adults in the USA, the researchers investigated the perception and effects of this change in CDC communication. The participants were assigned to different groups and either read the earlier version of the CDC communication (clear consensus), the newly introduced version (emphasised uncertainty) or no corresponding communication.

More doubts, less willingness to vaccinate
The results clearly show that those who read the modified communication rated vaccination side effects as more likely, expressed greater concerns about vaccination safety and were less willing to be vaccinated. According to a key finding of the study, the type of communication can itself become a risk factor. "It is not a question of concealing scientific uncertainty as a matter of principle. What is crucial is that it is communicated in a way that is consistent with the actual evidence, particularly on topics where there is already broad scientific consensus," says Professor Dr Cornelia Betsch. A declining willingness to be vaccinated can lead to more preventable diseases, a higher burden on the healthcare system and rising social costs.

Beyond the willingness to be vaccinated, the shift in communication by the CDC has had other social consequences: Study participants' trust in the CDC as an official state institution decreased, while at the same time approval of typical patterns of science denial, i.e. ways of thinking that favour disinformation, such as selective use of evidence, unrealistic demands for proof and even conspiracy-oriented thinking, increased.

High relevance for health communication
The study shows that changes in health communication are not mere formalities, but that they can have a real impact on trust, attitudes and behaviour. The authors therefore recommend documenting important changes in health messages transparently, carefully aligning them with the evidence and if possible checking in advance how they can be understood by the population. Uncertainty should always be categorised in communication in the context of the current state of research and combined with a clear recommendation for action.