US President Donald Trump signed an executive order on Monday calling for a sweeping overhaul of the childhood vaccine schedule, reducing the number of recommended immunisations and directing health authorities to explore splitting the combined measles, mumps and rubella (MMR) vaccine into three separate shots. The order cuts the list of recommended childhood vaccines from 18 to 11, removing guidance for hepatitis B, Covid-19 and influenza shots, and calls for all vaccinations to be spread across multiple doctor visits rather than administered together. Trump also repeatedly suggested — without evidence — that childhood vaccines are linked to autism, comparing the MMR shot to "a bottle of soda poured into a little child's body" and calling it potentially "quite lethal." When pressed for evidence, Trump said only: "What I've heard is that there are some people that say it is that way."

Multiple large-scale studies have found no causal link between vaccines and autism, including a 2019 Danish study of 657,461 children. The Centers for Disease Control and Prevention (CDC) states there is "no published scientific evidence that shows any benefit in separating the combination MMR vaccine into three individual shots," and notes that splitting the shots increases the risk of children contracting diseases in the interim or missing follow-up appointments. The individual component vaccines for measles, mumps and rubella are not currently available in the United States; the order directs the Department of Health and Human Services (HHS) to work with the private sector and other countries to develop them — a process experts say could take more than a decade. Crucially, the executive order serves as guidance rather than a mandate: in the US, requirements for school attendance vaccinations are set at the state level, not by the federal government.

The medical community responded with swift and sharp condemnation. The American Academy of Pediatrics (AAP) called the order "dangerous" and not based on "gold-standard science," warning that "delaying or skipping shots is risky, especially as measles continues to spread and children go back to school." The American College of Physicians described the changes as "problematic and deeply concerning," adding that splitting the MMR vaccine into multiple visits would raise costs for families and increase the logistical burden of childcare. The backlash was bipartisan: Republican Senator Bill Cassidy, a physician who cast the deciding vote to confirm Health Secretary Robert F. Kennedy Jr, wrote on social media that the order was "wrong," stating plainly: "Vaccines are overwhelmingly safe. Vaccines are effective. Vaccines DO NOT cause autism."

The order arrives at a particularly fraught moment for US public health. The country is currently experiencing its worst measles outbreak in 35 years, and Kennedy — who founded an anti-vaccine non-profit before joining the Trump administration — has been accused by critics of fuelling vaccine hesitancy and contributing to the crisis. Kennedy framed Monday's changes as expanding parental choice rather than restricting access. A federal court earlier this year blocked a previous attempt by the Trump administration to revise vaccine policy, siding with major medical organisations who argued the process was unlawful. Democratic lawmakers urged parents to disregard the executive order and follow the advice of their doctors rather than the White House. The AAP maintains that the current vaccine schedule is designed around when children's immune systems respond best and when they are most vulnerable to serious disease, and that there is no medical reason to delay or skip recommended immunisations.