Robert F Kennedy Jr wrong about mRNA vaccines’ effectiveness

The US health secretary Robert F Kennedy Jr announced on 5 August that his department would stop funding research into mRNA vaccines—and in doing so made misleading claims about them.

In a post on X, he said “We reviewed the science, listened to the experts, and acted […] because the data show these vaccines fail to protect effectively against upper respiratory infections like COVID and flu. We’re shifting that funding toward safer, broader vaccine platforms that remain effective even as viruses mutate.”

He went on to say in the attached video: “This dynamic drives a phenomenon called antigenic shift, meaning that the vaccine paradoxically encourages new mutations and can actually prolong pandemics as the virus constantly mutates to escape the protective effects of the vaccine.”

This is a misleading description of the effectiveness of the vaccines and how they work.

The vaccines have been proven to be highly effective against Covid-19 disease and Phase 3 trial results suggest that at least one mRNA vaccine is effective against flu.

The claim that mRNA vaccines encourage mutations in the virus is also misleading. The virus may evolve resistance to mRNA vaccines, but this happens in response to other vaccines too, as well as to natural immunity when people get infected.

Our conclusions about Mr Kennedy’s comments are shared by leading scientists around the world.

mRNA vaccines are very effective against Covid-19

Mr Kennedy’s claim that mRNA vaccines “fail to protect effectively” against Covid-19 is not supported by the evidence.

While mRNA Covid vaccines, such as the Pfizer and Moderna vaccines, do not completely prevent transmission, they have been proven to be highly effective, especially at making people much less likely to get severely ill or die from the disease.

More recent booster doses continue to provide some additional protection against newer variants in elderly people—even those who have been vaccinated or infected many times before—although this protection wanes over time.

Overall, it is estimated that these mRNA vaccines have saved millions of lives. Office for National Statistics (ONS) data shows that, in England, 63 deaths involving Covid vaccines were registered up to July 2023. But analysis from the UK Health Security Agency found that the vaccines prevented 127,500 deaths in England up to 24 September 2021.

Responding to Mr Kennedy’s announcement, a number of UK experts told the Science Media Centre that mRNA vaccines have been proven to be effective against Covid. The NHS says all Covid vaccines in use in the UK have met “strict standards” of effectiveness, as well as safety, while the US Centers for Disease Control and Prevention says that clinical trials have shown Covid vaccines are “safe and effective, especially against severe illness, hospitalization, and death”.

No mRNA vaccines against flu have been approved for use yet. But in June this year Moderna announced results of a phase three trial showing that its vaccine was about 27% more effective than standard flu vaccines in people over 50, and many other candidates are also currently in trials.

On this basis, it isn’t clear how Mr Kennedy could already know that this type of vaccine was not effective.

What about RFK’s claims about ‘mutations’?

In the video on his X post, Mr Kennedy, who has a history of vaccine scepticism, explained the rationale for the decision in more detail.

An antigen is something that produces an immune response in the body, whether it’s a pathogen or a vaccine. So Mr Kennedy seems not to be saying that mRNA vaccines fail to prevent people getting ill with Covid, but rather that they cause more problems later on by encouraging mutations.

A range of experts have said this argument is misleading, although the reasons why depend on exactly what he meant.

If Mr Kennedy’s claim that an mRNA vaccine “encourages new mutations” was intended to suggest that mRNA vaccines cause mutations, or make them more likely to occur, then this is not correct.

Mutations occur randomly in nature, including in viruses, but there is no known mechanism by which a vaccine might make mutations more likely.

Dr Peter Hotez, an expert in vaccine development told factcheck.org that no “single mutation” had ever rendered an mRNA vaccine ineffective. A specialist in infectious disease research, Dr Michael Osterholm, said: “The idea that it [the vaccine] drives the potential for mutations is simply not true.”

Alternatively, Mr Kennedy may have intended to suggest that mRNA vaccines encourage new viral variants to evolve through natural selection of the mutations that evade their protection. If so, this is misleading because while mRNA vaccines may have that effect, so too do other vaccines, as could natural immunity after an infection.

This happens because viruses—like all organisms—are under pressure to evolve resistance to anything that makes it harder for them to survive and replicate. So even though mutations occur randomly, the mutations that help a virus to avoid people’s immunity are more likely to accumulate over time, gradually changing the virus until it forms a new variant that can infect them more easily again.

This process happens constantly with seasonal flu, and it’s what we’ve also seen with Covid, which is why our vaccines against both diseases are updated regularly. (Strictly speaking, the process is called “antigenic drift”—not “shift”, the word Mr Kennedy used, which is generally reserved for the “an abrupt major change” such as when two different influenza viruses swap sections of their DNA.)

Professor Christopher Chiu, professor of infectious diseases at Imperial College London, told the Science Media Centre: “It is misleading to single out mRNA vaccines for promoting mutations and failing to protect against common cold-like symptoms; this is true for all respiratory virus vaccines that are given by injection and can stimulate a protective immune response.”

Professor Sir Andy Pollard, director of the Oxford Vaccine Group and outgoing chair of the Joint Committee on Vaccination and Immunisation, told us: “It could be argued that vaccination might improve immunity (while also stopping people ending up in hospital or dying) but also drive emergence of new variants. However, in the absence of vaccination, infection is widespread and also drives improved immunity against the current variant and therefore the emergence of new variants…In real life, this is a rather irrelevant point of discussion since the pressure on the virus caused by vaccination is rather trivial.”

Adam Finn, Professor of Paediatrics at the University of Bristol, told us: “The evolution (mutation followed by selection) of new variants is certainly driven by specific immunity within the human population—both due to infection and by vaccines—but it's a feature of the virus, not of the vaccines, whether mRNA or other platforms. The words that spring to mind are: Nonsense And Ignorance.”

What about RFK’s sources?

In its published statement, the US Department of Health and Human Services provided a link to what it said was data that it claimed would “show these [mRNA] vaccines fail to protect effectively against upper respiratory infections like COVID and flu”.

The 181-page document contains a long list of hundreds of scientific publications that the authors say relate to “COVID-19 mRNA vaccine harms”, and which “originated with the authors’ contributions to Toxic Shot: Facing the Dangers of the Covid ‘Vaccines’”. This refers to a book by Dr Byram Bridle, a Canadian academic whose claims about Covid-19 vaccines we and other fact checkers have written about many times before.

We have not been able to fully review every publication included in the document, but so far we have not found any clear evidence in it to support Mr Kennedy’s claims. Other articles reviewing the list of publications have also not found that it supports Mr Kennedy’s claims.

Erik Sass, the corresponding author of the list the department shared, told us that he believed the list did support Mr Kennedy’s claims, but he did not address our specific questions about some of the publications included in it.

Full Fact approached Dr Bridle and the Department of Health and Human Services for comment.

Thanks to Professor Peter Openshaw, a respiratory physician and mucosal immunologist at Imperial College London, for his help with this article.