Measles, Mumps, Rubella, and Varicella (MMRV) Vaccine

The safety record of MMRV vaccine is good. Most children who get the vaccine do not have any problems. As with all medicine, some problems – usually very minor – can happen. The MMRV vaccine sometimes causes mild problems such as fever, mild rash, or swelling of neck or cheek glands. On very rare occasions, the vaccine’s ingredients cause severe (anaphylactic) allergic reactions. Studies have also shown that children who get their first MMRV vaccine when they are 12-23 months old are about twice as likely to have a febrile seizure (seizure caused by a fever) 5-12 days following the shot, compared with those who get the MMR and varicella vaccines separately but at the same doctor visit. There has not been an increased risk of febrile seizures observed following vaccination with MMRV vaccine in children aged 4 to 6 years.

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How CDC Monitors the Safety of MMRV Vaccine

CDC and FDA monitor the safety of vaccines after they are licensed. Any problems detected with these vaccines will be reported to health officials, health care providers, and the public. Needed action will be taken to ensure the public’s health and safety.

CDC uses three systems to monitor vaccine safety:

The Vaccine Adverse Event Reporting System (VAERS)– an early warning system that helps CDC and FDA monitor problems following vaccination. Anyone can report suspected vaccine reactions and issues to VAERS.
The Vaccine Safety Datalink (VSD) – a collaboration between CDC and several health care organizations that allows ongoing monitoring and proactive searches of vaccine-related data.
The Clinical Immunization Safety Assessment (CISA) Project– a partnership between CDC and several medical centers that conduct clinical research on vaccine-associated health risks in certain groups of people.

A Closer Look at the Safety Data

Before the vaccine was licensed for use in the United States, studies were conducted in children aged 12 to 23 months old. The studies found that a fever of 102° F or higher and rash occurred more frequently during the 42 days after the first dose of MMRV vaccine compared with separate injections of MMR and varicella vaccines. Soreness at the injection site was reported less often after MMRV vaccine than after MMR and varicella vaccines given in separate shots at the same visit. For more information, see “Results from Studies Before MMRV Vaccine Was Licensed”.