Trump proposes separating MMR vaccine into three shots, experts say it lacks scientific basis

President Donald Trump issued an executive order calling for the measles, mumps and rubella (MMR) vaccine to be administered as three separate injections. The proposal has been dismissed by medical experts, who say there is no scientific evidence that separating the vaccine improves safety or efficacy.

Trump claimed the combined shot could be "quite lethal," a statement that public-health professionals described as unfounded. Neil Maniar, a professor of public health at Northeastern University, said splitting the vaccine would create "significant logistical limitations" and could lead to delayed or missed vaccinations.

Andrew Racine, president of the American Academy of Pediatrics, noted that vaccine hesitancy has already contributed to a rise in measles cases, the highest in decades. William Moss, a pediatrician and epidemiology professor at Johns Hopkins University, warned that the proposal could further erode public confidence in the MMR vaccine.

Experts highlighted that the current two-dose schedule—first dose at 12 to 15 months and a second at 4 to 6 years—has been shown to improve completion rates. Separating the vaccine could require up to six visits in early childhood, increasing the burden on families and health-care systems, especially in rural areas.

Manufacturers Merck and GSK indicated that combination shots have higher compliance and that developing separate monovalent vaccines would take years and substantial investment, with little commercial incentive. Both Racine and Moss said it would likely take more than a decade to bring standalone shots to market, if at all.

Public-health officials emphasized that the existing schedule is designed around immune system readiness and disease risk, and that altering it without evidence could create new barriers to vaccination rather than solving any problem.