Trump issues order to split MMR vaccine into three separate shots, sparking medical criticism

President Donald Trump signed an executive order this week recommending that the measles, mumps and rubella (MMR) vaccine be divided into three separate injections administered at different visits. The order has been met with opposition from physicians and public-health organizations, which point to decades of research showing the combined vaccine is safe and effective.

Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, warned that separating the vaccine would increase the number of required appointments from two to six, creating a higher risk that children miss doses during the current rise in measles cases. "If you separate the vaccine into its three component parts, you have to have six shots instead of two, which makes it more burdensome and difficult," he said.

Experts noted that no monovalent measles, mumps or rubella vaccines are currently licensed in the United States, and developing them would entail extensive research, clinical trials and regulatory approval. Merck, the maker of the MMR II vaccine, said there is no published scientific evidence showing any benefit from splitting the combination shot and cautioned that more injections could lead to delayed or missed immunizations.

Public-health officials also emphasized that the combined MMR vaccine, in use since 1971, provides protection comparable to separate doses and that two doses achieve 97% effectiveness against measles and 88% against mumps. They argued that the proposed change would add logistical strain on families and pediatric practices without improving vaccine safety.

During the signing ceremony, Trump and Health Secretary Robert F. Kennedy Jr. repeated unsubstantiated claims linking vaccines to autism and suggesting that the U.S. administers more childhood vaccines than peer nations. These assertions have been repeatedly refuted by scientific studies and meta-analyses, which find no connection between the MMR vaccine and autism and indicate that modern vaccines contain fewer antigens than those used in earlier decades.