Acting CDC director calls to 'break up' the measles, mumps and rubella vaccine into three shots

Acting CDC Director Jim O’Neill called on vaccine manufacturers to develop separate shots for measles, mumps and rubella instead of the current combination vaccine.

Acting CDC Director Jim O’Neill on Monday called on vaccine manufacturers to develop separate shots for measles, mumps and rubella instead of the current vaccine, which combines the three.

O’Neill wrote in a post on X that manufacturers should replace the MMR vaccine with “safe monovalent vaccines,” which only target one virus. His statement referenced a recent comment from President Donald Trump, who advised people last month on Truth Social to “break up the MMR shot into three totally separate shots.”

However, no monovalent vaccines for measles, mumps or rubella are approved in the U.S., and the Centers for Disease Control and Prevention says there is no published scientific evidence that shows a benefit to separating the combined vaccine. It is not clear whether the change O'Neill is calling for is possible or likely to come about.

Andrew Nixon, a spokesperson for the Department of Health and Human Services, said “standalone vaccinations can potentially reduce the risk of side effects and can maximize parental choice in childhood immunizations.” He did not offer evidence for his statement about side effects.

The measles, mumps and rubella vaccine has been available as a combination shot since 1971, in part to reduce the number of injections that children receive, given that the three are administered at the same ages.