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 several countries and looked both at vaccines in general and at those containing thimerosal – 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 “confirming the absence of a causal relationship with autism spectrum disorders”.
Experts also reviewed concerns about certain vaccines that contain very small amounts of aluminum salts, which help the body mount a stronger immune response.
This assessment was based 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 aluminum used in some vaccines and ASD”, stressing that these ingredients have been used safely for many decades.
After the review, the group confirmed previous findings issued in 2002, 2004 and 2012: “Vaccines, including those with thiomersal and/or aluminum, do not cause autism.”
The WHO urged governments to ensure that vaccine policies remain grounded in science, noting that “global childhood vaccination efforts represent one of the greatest achievements in improving lives, livelihoods and prosperity in societies”.
Over the past 50 years, the WHO estimates that vaccines have saved at least 154 million lives.
Debate in the United States
The update follows a WHO statement issued on 24 September following renewed political debate in the US. This statement warned against reviving discredited theories linking vaccines to autism, stressing that “a robust, comprehensive evidence base exists to show that childhood vaccines do not cause autism”.
Studies suggesting otherwise, the WHO said at the time, were flawed and have long been debunked.
The 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 to review new evidence and advise countries based on the strongest available science.
