NAIROBI, Kenya – The World Health Organisation (WHO) has dismissed renewed claims linking vaccines or common painkillers to autism, saying there is no scientific evidence to support such assertions.
In a statement issued after a fresh wave of misleading social media posts circulating globally — including in Kenya — the UN health agency said extensive research has consistently shown that vaccines do not cause autism spectrum disorder (ASD).
“Based on available evidence, no causal link exists between vaccines and autism spectrum disorders,” WHO said, reaffirming its long-held position that childhood vaccines are safe.
The clarification follows claims suggesting that routine immunisations, or the use of paracetamol during pregnancy, could trigger autism — allegations scientists have repeatedly debunked.
Extensive global review
WHO said its findings are based on an analysis by the Global Advisory Committee on Vaccine Safety (GACVS), an independent panel established in 1999 to assess vaccine safety concerns.
According to the organisation, the committee reviewed 31 major research studies published between January 2010 and August 2025, drawing on data from multiple countries.
“Evidence from these studies strongly supports the positive safety profile of vaccines used during childhood and pregnancy and confirms the absence of a causal link with ASD,” the WHO said.
The review also examined long-standing concerns around thiomersal — a preservative previously used in some vaccines — and aluminium, which is added in small quantities to certain vaccines to boost immune response.
WHO said it assessed studies dating from 1999 to March 2023, including a large Danish study involving children born between 1997 and 2018.
“In summary, the available high-quality evidence shows no association between the trace amounts of aluminium used in some vaccines and ASD,” the agency said, adding that vaccines containing aluminium adjuvants remain safe.
As a result, WHO reaffirmed earlier conclusions reached in 2002, 2004 and 2012 that vaccines, including those containing thiomersal or aluminium, do not cause autism.
Paracetamol claims also rejected
The organisation also addressed claims linking autism to the use of paracetamol (acetaminophen) during pregnancy.
In a separate statement issued in September, WHO said there is currently no conclusive scientific evidence establishing a link between autism and the use of paracetamol by expectant mothers.
“Researchers have spent the last decade examining this possible association, but no consistent link has been established,” the agency said.
WHO estimates that autism affects about 62 million people worldwide, noting that the exact causes of the condition remain unclear and are believed to involve multiple factors related to brain development.
Autism is a developmental condition — not a disease — that affects how individuals communicate, interact with others and experience their environment.
Children with autism may learn or communicate differently, display repetitive behaviours, or prefer structured routines.
Kenya context
Kenya has one of the highest vaccine uptake rates globally. National health data show that about 80 per cent of children aged 12 to 23 months were fully vaccinated with key routine immunisations before the Covid-19 pandemic.
However, Kenya does not yet have official national statistics on autism prevalence due to limited large-scale research and the absence of a dedicated surveillance system.
Parent-led organisations, including the Autism Society of Kenya, estimated in 2023 that autism could affect about four per cent of the population — roughly 2.2 million people — though the figures are based on community reports rather than formal national surveys.
WHO urged governments to base immunisation policies on robust scientific evidence, noting that vaccination has transformed global health and saved an estimated 154 million lives over the past 50 years.
