Meeting on 27 November, the WHO Global Advisory Committee on Vaccine Safety examined 31 major research studies published between 2010 and August 2025.

The analysis covered data from multiple countries and looked both at vaccines in general and at those containing thiomersal – a preservative sometimes used to prevent contamination in multi-dose vials.

‘Positive safety profile’

According to the committee, the latest review “strongly supports the positive safety profile of vaccines used during childhood and pregnancy” and “confirms the absence of a causal link with autism spectrum disorders”.

Experts also reviewed concerns about certain vaccines that contain very small amounts of aluminium salts, which help the body create a stronger immune response.

This assessment drew on studies published over more than two decades, as well as a large national study from Denmark that tracked children born between 1997 and 2018.

The WHO committee concluded that the evidence “shows no association between the trace amounts of aluminium used in some vaccines and ASD”, stressing that these ingredients have been used safely for many decades.

Following the review, the group reaffirmed earlier findings issued in 2002, 2004 and 2012: “Vaccines, including those with thiomersal and/or aluminium, do not cause autism.”

WHO urged governments to ensure that vaccine policies remain rooted in science, noting that “global childhood immunisation efforts represent one of the greatest achievements in improving lives, livelihoods and the prosperity of societies”.

Over the past 50 years, WHO estimates that vaccines have saved at least 154 million lives.

Debate in the US

The update follows a WHO statement issued on 24 September, following renewed political debate in the United States. That statement warned against reviving discredited theories linking vaccines to autism, stressing that “a robust, extensive evidence base exists showing childhood vaccines do not cause autism”.

Studies suggesting otherwise, WHO said at the time, were flawed and have long been debunked.

WHO reiterated that decades of independent research reach the same conclusion: vaccines are safe, effective and critical to public health.

The organization said it will continue reviewing emerging evidence and advising countries based on the strongest available science.