On Sept. 6, 2005, the MMRV vaccine was licensed in the United States and may be used instead of measles, mumps, rubella vaccine (MMR, M-M-RII, Merck & Co.) and varicella vaccine (VARIVAX, Merck & Co.) to implement the recommended 2-dose vaccine schedule for prevention of measles, mumps, rubella, and varicella among children aged 12 months–12 years.

At the time of its licensure, use of MMRV vaccine was preferred for both the first and second doses over separate injections of equivalent component vaccines (MMR vaccine and varicella vaccine), which was consistent with ACIP’s 2006 general recommendations on use of combination vaccines (CDC. General recommendations on immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2006;55;[No. RR-15]). Since July 2007, supplies of MMRV vaccine have been temporarily unavailable as a result of manufacturing constraints unrelated to efficacy or safety. MMRV vaccine was expected to be available again in the United States in May 2010.

The final results of the two postlicensure studies indicated that among children aged 12–23 months, one additional febrile seizure occurred 5–12 days after vaccination per 2,300–2,600 children who had received the first dose of MMRV vaccine compared with children who had received the first dose of MMR vaccine and varicella vaccine administered as separate injections at the same visit. Data from postlicensure studies do not suggest that children aged 4–6 years who received the second dose of MMRV vaccine had an increased risk for febrile seizures after vaccination compared with children the same age who received MMR vaccine and varicella vaccine administered as separate injections at the same visit.