• Posted October 7, 2025

Interim CDC Chief Calls for Separate MMR Shots

The acting head of the U.S. Centers for Disease Control and Prevention (CDC) is calling on vaccine makers to create separate measles, mumps and rubella (MMR) shots, though public health experts saying there’s no scientific reason to do so.

“I call on vaccine manufacturers to develop safe monovalent vaccines to replace the combined MMR and ‘break up the MMR shot into three total separate shots’,” Jim O’Neill, who is also deputy secretary of the U.S. Department of Health and Human Services (HHS), wrote Monday on X.

His post echoed a Sept. 26 post from President Donald Trump, who has also called for dividing up the combination vaccine.

The MMR vaccine has been given as a combo in the U.S. since 1971. The CDC’s website says there is “no published scientific evidence” showing any benefit to separating it.

Separating the MMR vaccine into three shots would “not make that vaccine safer,” Dr. Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia, told CNN. “It would just make it more expensive and less likely to be used.”

A spokesperson for Merck, which manufactures one of the two approved MMR vaccines in the U.S., said combination vaccines are designed to meet public health needs by protecting against multiple diseases with fewer injections.

“Use of the individual components of combination vaccines increases the number of injections for the individual and may result in delayed or missed immunizations,” the spokesperson told CNN.

GSK, the other approved MMR vaccine maker, agreed. 

“Combination vaccines play a crucial role in improving vaccination coverage rates; their safety and efficacy have been demonstrated by decades of research," GSK said in a statement. "By reducing the number of separate injections required, combination vaccines allow for a simpler and more efficient immunization process, which is essential for timely protection against disease."

The idea of splitting up the MMR vaccine isn't new. It gained attention in the late 1990s after a now-retracted paper suggested a link between the MMR shot and autism.

“Before the claim was discredited, researchers took it seriously, investigated it thoroughly, and found no link,” the American Academy of Pediatrics (AAP) said. “This research, in many countries, involving thousands of individuals, has spanned multiple decades.”

Despite this, Trump emphasized his call for separate doses last month during a White House event about autism, saying, “the MMR, I think, should be taken separately. This is based on what I feel.”

The CDC continues to recommend two doses of the MMR vaccine, the first at around age 1 and the second between ages 4 and 6. The agency also notes that combo vaccines are safe and help prevent delays in immunization.

While the varicella (chickenpox) vaccine is sometimes given as a combination with MMR, CDC guidance recommends giving the first doses separately for children under 4 due to a small risk of febrile seizures. However, the combination is still considered safe for older children.

More information

Children's Hospital of Philadelphia has more on measles, mumps and rubella.

SOURCE: CNN, Oct. 6, 2025