Trump signs executive order seeking to split MMR vaccine into separate shots

President Donald Trump signed an executive order on August 10, 2026, seeking to reduce universally recommended childhood vaccines from 17 to 11 and split the combined MMR vaccine into three separate shots. Public health experts, medical associations, and vaccine manufacturers like Merck strongly oppose the move, warning it lacks scientific basis and will lead to missed doses. Critics, including Republican Senator Bill Cassidy, emphasize that the changes could worsen ongoing measles outbreaks by creating logistical barriers for families.

Trump MMR vaccine executive order

• ▪The executive order signed by President Donald Trump on August 10, 2026, directs that the combined measles, mumps, and rubella vaccine be split into three separate shots once they are domestically available
• ▪U.S. President Donald Trump signed an executive order on August 10, 2026, calling for the childhood immunization schedule to be reduced from 17 universally recommended shots to 11
• ▪President Donald Trump's August 10, 2026, executive order directs that, to the maximum extent feasible, all childhood vaccines be administered at separate medical appointments

Insufficient scientific evidence

• ▪Numerous scientific studies and public health authorities have found no evidence linking the measles, mumps, and rubella vaccine, or the preservative thimerosal, to autism
• ▪The Trump administration's vaccine schedule review, led by Tracy Beth Høeg and Martin Kulldorff, contended that the current U.S. schedule is partly responsible for declining vaccination rates
• ▪President Donald Trump claimed without evidence that the combined measles, mumps, and rubella vaccine could be lethal, though he later acknowledged having no evidence for the claim

Historical MMR vaccine development

• ▪The mumps vaccine strain still used in the United States was developed by scientist Maurice Hilleman in 1967 using a virus isolated from his daughter, Jeryl Lynn
• ▪Japan suspended its combined MMR vaccine in 1993 due to meningitis concerns, leading to a drop in measles vaccination rates to 83% in 2001 and an outbreak affecting 265,000 children
• ▪Maurice Hilleman combined individual mumps, measles, and rubella vaccines to create the combined MMR vaccine, which was licensed in the United States in 1971

Missed vaccination risks

• ▪Public health experts warn that splitting the MMR vaccine and requiring separate medical visits will increase logistical barriers, leading to delayed or missed childhood immunizations
• ▪The U.S. kindergarten MMR vaccination rate fell to 92.5% in the 2024–25 school year, which is below the 95% threshold required to maintain community protection
• ▪A Stanford modeling study estimated that a 10% decrease in MMR vaccination coverage in the United States would result in 11 million measles cases over 25 years

Malleable middle parent group

• ▪A June poll by KFF found that 31% of U.S. adults fall into a malleable middle group who are uncertain about vaccines and highly receptive to misinformation
• ▪A 2025 survey by KFF and the Washington Post found that approximately 9% of parents reported either skipping or delaying the MMR vaccine for their children

Industry pushback on changes

• ▪The American College of Physicians and the American Academy of Pediatrics criticized the executive order, stating it lacks scientific evidence and threatens public health
• ▪Republican Senator Bill Cassidy, a physician who chairs the Senate Health Committee, publicly criticized the executive order, stating that breaking up vaccines will require children to get more shots
• ▪Vaccine manufacturers Merck and GSK have expressed no interest in developing monovalent measles, mumps, and rubella vaccines, noting that combination shots improve compliance