The US Centers for Disease Control and Prevention (CDC) has called for the development of separate vaccines for measles, mumps and rubella, replacing the combined MMR shot, despite the country facing its worst measles outbreak in decades. The request, made by Jim O’Neill, deputy secretary of Health and Human Services and acting CDC director, has sparked alarm among public health experts who warn it could reduce vaccination rates and increase costs.
O’Neill posted on X/Twitter on Monday urging manufacturers to create safe monovalent vaccines, citing a previous statement by Donald Trump opposing mixed vaccines. The combined MMR vaccine has been used for decades to reduce the number of shots children receive, and its safety and efficacy are well-established. Experts argue that splitting the vaccine would be unnecessary, costly, and time-consuming.
Jason Schwartz, an associate professor at Yale School of Public Health, said breaking up the MMR vaccine would require more visits to pediatricians, making it harder for parents to complete the full schedule. “Splitting up will mean that fewer kids will complete the MMR series,” he warned. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, called the move pointless and noted that some vaccines, like DTaP, cannot be separated.
Currently, only combined MMR shots are available in the US, made by Merck and GSK. Both companies stated there is no scientific evidence to support separating them. Developing new monovalent vaccines would require entirely new clinical trials, which experts deem unethical as they would expose infants to potentially lethal diseases. Angela Rasmussen, a virologist at the University of Saskatchewan, said such trials would not be approved by ethics boards.
The CDC’s advisory committee on immunization practices (ACIP) had a meeting planned for 22-23 October, which has been indefinitely postponed. At a previous meeting in September, advisers discussed delaying the hepatitis B vaccine but tabled the discussion. Offit expressed concern that decisions are being driven by anti-vaccine notions rather than scientific data.
