Vaccines 2025

The Centers for Disease Control and Prevention (CDC) vaccine advisory group has revised its recommendations regarding the combined measles, mumps, rubella, and varicella (MMRV) vaccine for the youngest children. The decision aligns with ongoing efforts by Health and Human Services (HHS) Secretary Robert F. Kennedy Jr. to reassess childhood vaccination policies and schedules. The change is driven by evidence of an elevated risk of febrile seizures, seizures triggered by fever,  when the combined vaccine is administered as the first dose in children under four years of age.
Scientific studies provide consistent support for this concern. When the MMRV vaccine is used instead of separate MMR and varicella vaccines, the excess risk corresponds to approximately one additional febrile seizure for every 2,300 doses administered, or about 4.3 seizures per 10,000 doses (1). Another study reported a relative risk of about 2.2 for febrile convulsions in children given the first dose of MMRV compared with those receiving separate MMR and varicella vaccinations (2). A meta-analysis further confirmed that children aged 10–24 months receiving MMRV as the first dose face a statistically significant increased risk of febrile seizures compared with separate administration (3). Most recently, updated safety data presented to the Advisory Committee on Immunization Practices (ACIP) reaffirmed these findings, showing that the elevated seizure risk is particularly relevant in children under four years old when MMRV is given as the initial dose (4).
In this case, it would be fair to ask whether Secretary RFK’s policy is truly misguided when it is driven by concern for public health rather than the “welfare” of pharmaceutical companies.

1. Klein NP, Fireman B, Yih WK, Lewis E, Kulldorff M, Ray P, Baxter R, Hambidge S, Nordin J, Naleway A, Belongia EA. Measles-mumps-rubella-varicella combination vaccine and the risk of febrile seizures. Pediatrics. 2010 Jul 1;126(1):e1-8.
2. Jacobsen SJ, Ackerson BK, Sy LS, Tran TN, Jones TL, Yao JF, Xie F, Cheetham TC, Saddier P. Observational safety study of febrile convulsion following first dose MMRV vaccination in a managed care setting. Vaccine. 2009 Jul 23;27(34):4656-61.
3. Ma SJ, Xiong YQ, Jiang LN, Chen Q. Risk of febrile seizure after measles–mumps–rubella–varicella vaccine: A systematic review and meta-analysis. Vaccine. 2015 Jul 17;33(31):3636-49.
4. “MMRV Vaccine Recommendations and Safety Review: Policy Recommendations Briefing (CDC, Sept 2025).” https://www.cdc.gov/acip/downloads/slides-2025-09-18-19/policy-recs-mmrv-briefing-508.pdf