select search filters
briefings
roundups & rapid reactions
Fiona fox's blog
Scientists respond to reports of comments made by President Trump about vaccines, MMR and autism when speaking about an Executive Order.
Prof Helen Bedford, Professor of Child Public Health, UCL Institute of Child Health, UCL, said:
“MMR vaccine has been used in the USA for over 50 years since the early 1970s and in the UK since 1988. It is highly effective and has an excellent safety profile. Like all vaccines, it can give rise to mild side effects such a fever, feeling off colour and as it is a live vaccine, symptoms of mild measles, mumps and rubella; these are innocuous, short lasting and not infectious. Occasionally side effects are more severe such a fits. The side effects of vaccines need to be balanced against the impact and complications of the diseases they prevent. Measles, mumps and rubella all have serious effects. We have already seen child deaths from measles this year in UK. A large body of research conducted over the past two decades has found strong evidence of no link between MMR vaccine and autism. The vaccine has, and continues to save, millions of lives. The three vaccines have never been administered as separate doses to young children as part of vaccination policy so that policy’s safety and effectiveness are unproven. However, just by delaying protection it would be a serious step backwards for protecting our children’s health.”
Dr Ben Kasstan-Dabush, Assistant Professor in Global Health & Development, London School of Hygiene & Tropical Medicine, said:
“The Measles, Mumps, Rubella (MMR) vaccination has a proven track record of being highly safe, effective and well tolerated, and Wakefield’s claim of a link to autism robustly rejected as a fabrication. Measles-containing vaccination, in particular, is credited with having the greatest contribution to reducing child deaths, sickness, and disability of any vaccination over the past 50 years.
“There is no evidence that offering the MMR vaccination as single injections is a safer or more effective method of immunising children. To the best of my knowledge there is no country that offers single injections as part of their national vaccination schedules, making the decision taken in the US to recommend splitting the MMR vaccination an experiment rather than an evidence-based decision.
“This move will further obstruct efforts to contain measles outbreaks that have persisted in the US, where there have been 2,465 confirmed measles cases reported as of 6 August 2026 and three deaths linked to measles in 2025. The Trump administration have a responsibility to explain how their latest recommendations will help to contain these outbreaks and the consequences for families. There is a very real risk that single injections will lead to decreased vaccination uptake, and would put more children at risk of vaccine preventable-diseases.
“UK families should be reassured that recommendations made by the Joint Committee for Vaccines and Immunisation are firmly rooted in evidence. The NHS vaccination schedule recommends that children receive two MMR/MMRV doses, administered alongside other vaccinations. At no point in the schedule is a child called in to a GP surgery to receive only one vaccination. Single injections would involve parents bringing their children for at least 6 separate appointments (or 8 in the case of MMRV). This would increase the risk of exposure to vaccine-preventable diseases, because children would need additional time to be brought up to schedule, and the burden on primary care teams as they need to offer more appointments per child.
“Offering single vaccinations may also influence parental risk perceptions, and lead parents to getting one vaccine (e.g. measles) for their child but not another (e.g. rubella). This scenario would be dangerous because children would not complete the full course of MMR vaccination so that they would not be protected, while also eroding population immunity and increasing the risks to those who cannot be vaccinated.”
Prof Sir Andrew Pollard, Director of the Oxford Vaccine Group and Ashall Professor of Infection and Immunity, Pandemic Sciences Institute and Department of Paediatrics, University of Oxford, said:
“The US administration’s decision to reduce the number of vaccines recommended for children, deprioritising jabs with a proven track record of effectiveness against serious diseases, and questioning the proven safety of vaccines in the process, undermines public confidence in the cornerstone of child health in the country. Vaccine programmes have been built by scientific evidence over decades and introduction of vaccines that make up a programme takes account of a country’s disease risk, health system and population demographics to make the best decisions to minimise serious illness and death in the population, and to assess affordability for the health system. These interventions are extensively tested and monitored, which is why we know that vaccines do not cause autism. The US immunisation programme saved an astonishing 1.1million lives in the country in the past 30 years (1994-2023), according to US Centers for Disease Control estimates. Changes in vaccination programmes can be appropriate when disease risk changes or new evidence emerges, but such changes should be driven by scientific evidence developed by individuals with the necessary expertise and not by whim, because the lives of children are at stake.”
Prof Michael Absoud, Professor of Paediatric Neurodevelopmental Disability, Faculty of Life Sciences & Medicine, King’s College London, said:
“The scientific evidence does not support a causal link between the MMR vaccine and autism.
“Large population studies and systematic reviews involving millions of children have found no increased risk of autism after MMR vaccination.
“One reason the MMR vaccine has been wrongly suspected is that the first dose is given at around the same age when early autistic differences, including slowing or loss of skills in some children, may first become apparent to parents.
“Temporal association is not the same as causation, and the fact that autistic features may become more noticeable in the second year of life does not mean that a vaccine given around that time caused autism.
“The original 1998 Lancet paper that suggested a link between MMR, bowel symptoms and autism was based on a very small and highly selected sample, was later retracted, and has been found to have involved serious scientific and ethical failings.
“The subsequent evidence has moved strongly in the opposite direction: carefully conducted epidemiological studies have not found that MMR causes autism.
“Autism diagnoses are more common now than decades ago, but this does not mean vaccines are the cause.
“The increase in autism diagnosis is best understood as reflecting multiple factors, including broader diagnostic criteria, greater awareness, improved recognition in children previously missed, and changes in clinical and educational practice.
“Autism is a highly heterogeneous neurodevelopmental condition with strong genetic contributions and smaller complex prenatal and perinatal influences; it is absolutely not explained by a single postnatal exposure such as MMR.
“Like all medicines, vaccines can have side effects, but serious adverse reactions to MMR are very rare, and the risks of measles, mumps and rubella themselves are substantially greater.
“Measles is not a trivial childhood illness: it is highly infectious and can cause pneumonia, encephalitis, long-term disability and death.
“Splitting MMR into separate measles, mumps and rubella vaccines is not supported by evidence as safer or better.
“Separating vaccines can leave children unprotected for longer and increases the risk that some children will not complete the full course.”
Declared interests
Prof Helen Bedford: “No conflicts.”
Dr Ben Kasstan-Dabush: “No conflict of interest to declare.”
Prof Sir Andrew Pollard: “Director of the Oxford vaccine group and former chair of JCVI.”
Prof Michael Absoud: “No conflicts.”