WHO reviews 15 years of vaccine research: still no link to autism

What happened

On 3 September 2026, the World Health Organization published a new evidence review called 'Vaccines, thiomersal and autism spectrum disorder: evidence review 2010-2025'. The WHO is the United Nations agency responsible for global health. When it publishes a review like this, it is pulling together the research that already exists rather than running a brand new experiment. That is an important difference, and we will come back to it. The review looked at peer-reviewed studies published between 2010 and August 2025. 'Peer-reviewed' means other scientists checked the work before it was published. The team paid particular attention to thiomersal, sometimes spelled thimerosal. Thiomersal is a preservative that contains a form of mercury. It has been used in some vaccines to stop bacteria growing in multi-dose vials. The question the review set out to answer was simple to ask and hard to study: do vaccines, including ones containing thiomersal, cause autism spectrum disorder? The WHO's answer was clear. In its own words, 'the most methodologically rigorous primary studies do not support a causal association between vaccines, including thiomersal-containing vaccines, and ASD'. This is not the first time the question has been asked. In December 2025, the WHO's Global Advisory Committee on Vaccine Safety published a statement reaching a similar conclusion. The new review is a fuller look at the published evidence behind that position.

Why this matters

The idea that vaccines might cause autism has been around since the late 1990s. It has been studied a great deal since then. Despite that, the worry has not gone away, and it still puts some parents off vaccinating their children. That matters because vaccines only work well when enough people have them. Diseases like measles spread very easily. When fewer children are protected, outbreaks become more likely. Measles is not a mild illness for everyone. It can cause serious complications, including swelling of the brain. So a review like this is not really about settling an argument on the internet. It is about giving parents, carers and health staff something solid to stand on when they make a decision. It also matters because of who is saying it. The WHO is not a vaccine manufacturer and does not sell vaccines. Its advisory committee on vaccine safety is made up of independent experts. When a body like that reviews 15 years of research and reaches the same conclusion that other reviews have reached, that is worth paying attention to. There is a second reason this is useful. It puts a date on things. Anyone can now point to a review that covers studies up to August 2025, rather than relying on older summaries.

What the evidence actually says

It is worth being precise here, because precision is what makes this kind of review trustworthy. The WHO did not say that every single study ever published found no link. It said something more careful and more useful than that. First, it said the strongest studies found no causal link. 'Causal' means one thing actually brings about the other, rather than the two simply appearing around the same time. Second, it looked at the studies that did report a positive association, meaning studies that seemed to find a link. The WHO judged that these had 'very low strength of evidence and high risk of bias'. Risk of bias means there were problems with how the study was designed or carried out that could push the result in a particular direction. Third, it looked at meta-analyses. A meta-analysis combines the results of many studies to get a bigger picture. The WHO reported that none of the meta-analyses it included supported a causal relationship. Its overall summary was that 'the evidence continues to support the safety of current vaccines with respect to ASD and other NDD'. NDD means neurodevelopmental disorders, a broader group that includes autism. There is one more piece of context that often gets missed. Timing can look convincing when it is not. Autism is usually identified in early childhood, at roughly the same age children receive several routine vaccines. Two things happening around the same time is not the same as one causing the other. Large studies are designed specifically to tell those two situations apart, and that is what they have done. It is also fair to say what this review does not do. It does not explain what causes autism. Research into that continues, and current evidence points strongly towards genetic factors alongside influences before birth. A review about what does not cause something cannot tell you what does.

Qurexa perspective

We deliver prescriptions and support people with taking their medicines, so we know that questions about safety rarely arrive at a convenient moment. They come up at the kitchen table, or in a queue, or late at night after reading something worrying. One thing we would gently point out: your community pharmacist is one of the most accessible healthcare professionals in the UK. You usually do not need an appointment. They are trained in medicines and vaccines, and they are used to being asked difficult questions without judging anyone for asking. If something you have read has left you unsure, asking a pharmacist is a reasonable and sensible next step. It costs nothing, and it is a far better source than a comment thread.

Practical advice

If you are trying to make sense of vaccine information, here are some steps that genuinely help. Check who is behind the claim. Look for the WHO, the NHS, the UK Health Security Agency, or the Medicines and Healthcare products Regulatory Agency. These bodies publish their reasoning, not just their conclusions. Look for a date. Science moves. A page with no date, or one from many years ago, may have been overtaken by newer work. Be careful with single studies. One study on its own is a piece of a puzzle, not the finished picture. Reviews and meta-analyses that pull many studies together are usually more reliable. Watch for strong emotional language. Careful research tends to sound measured. Words designed to frighten or enrage are a signal to slow down and check. Write your questions down before an appointment. It is easy to forget them once you are in the room. Ask about your own situation specifically. General advice is a starting point, but your GP or pharmacist can talk about your family's circumstances, including any allergies or health conditions. If you have missed vaccinations, it is usually not too late. Speak to your GP practice about catching up rather than assuming the chance has gone.

What to know

The WHO published a review on 3 September 2026 covering peer-reviewed research from 2010 to August 2025 on vaccines, the preservative thiomersal, and autism. Its finding was that the strongest studies do not support a causal link. Studies that appeared to find one were judged to have very low strength of evidence and a high risk of bias, and none of the meta-analyses included supported a causal relationship. This is consistent with the position taken by the WHO's Global Advisory Committee on Vaccine Safety in December 2025. If you have questions about a vaccine for yourself or your child, your GP practice or community pharmacist can talk them through with you. Sources: World Health Organization, 'Vaccines, thiomersal and autism spectrum disorder: evidence review 2010-2025', 3 September 2026, https://www.who.int/publications/i/item/vaccines--thiomersal-and-autism-spectrum-disorder--evidence-review-2010-2025 | World Health Organization, 'Statement of the WHO Global Advisory Committee on Vaccine Safety (GACVS) on vaccines and autism', 11 December 2025, https://www.who.int/news/item/11-12-2025-statement-gacvs-vaccines-autism | World Health Organization, 'WHO expert group's new analysis reaffirms there is no link between vaccines and autism', 11 December 2025, https://www.who.int/news/item/11-12-2025-who-expert-group-s-new-analysis-reaffirms-there-is-no-link-between-vaccines-and-autism This article is for general information and does not replace advice from a doctor, pharmacist or other qualified healthcare professional. If you have questions about vaccination for yourself or your child, please speak to your GP practice or pharmacist.