Vaccine Makers and Experts Reject Trump’s Push to Split MMR Shot

President Donald Trump’s executive order calls for splitting the measles, mumps and rubella (MMR) vaccine into three separate shots, but manufacturers Merck and GSK, along with doctors and public health experts, say there is no scientific evidence supporting this change and that the combined MMR vaccine has decades of proven safety and efficacy.

Merck and GSK state that developing separate monovalent measles, mumps, and rubella vaccines would require years—potentially up to a decade—of regulatory approval, clinical trials, and manufacturing setup, and they show little interest in pursuing such a move given the lack of demonstrated benefit.

Experts warn that splitting the MMR vaccine would increase the number of injections, office visits, and overall costs, while also raising the risk of delayed or missed immunizations, which could leave children vulnerable to measles, mumps, and rubella in the interim.

The CDC and major medical associations emphasize that there is 'no published scientific evidence' showing any benefit from separating the MMR vaccine and that Trump’s push is not based on current science but on political and parental concerns, including unfounded fears about autism and vaccine safety.

Despite Trump’s order and associated calls from administration officials, neither Merck nor GSK has announced plans to develop or license separate measles, mumps, and rubella vaccines in the United States, and experts view the directive as largely symbolic or aspirational rather than immediately implementable.