News & Views

Press Release

Twelve-Year Study Confirms Overall Safety of Measles Vaccines

January 5, 2015

woman physician examining an infant being held by the mother

OAKLAND, Calif. — A 12-year study of two measles-containing vaccines, published today in Pediatrics, found that seven main adverse outcomes were unlikely after either vaccine.

The study, conducted by the Kaiser Permanente Vaccine Study Center, included children aged 12 to 23 months, from January 2000 through June 2012, who received measles-mumps-rubella-varicella (or MMRV) or separately administered, same-day measles-mumps-rubella and varicella (or MMR + V) vaccines. A total of 123,200 MMRV doses and 584,987 MMR + V doses were evaluated.

Comparing MMRV with MMR + V found no increased risk of seven main neurological, blood or immune system disorders (immune thrombocytopenia purpura, anaphylaxis, ataxia, arthritis, meningitis/encephalitis, acute disseminated encephalomyelitis and Kawasaki disease). No new safety concerns were identified after either vaccine, and most outcomes studied were unlikely after either vaccine.

“This study did not identify any new safety concerns comparing MMRV with MMR + V or after either the MMRV or the MMR + V vaccine,” said lead author Nicola P. Klein, MD, PhD, co-director of the Vaccine Study Center. “In fact, there were few or zero events for several outcomes following vaccination. These findings indicate that even if an increased risk for these outcomes exists, the risk is low and rare. This should reassure parents that these outcomes are unlikely after either vaccine.”

The study also confirmed the findings from previous studies that MMRV and MMR + V are associated with fever and febrile seizure seven to 10 days after vaccination among 1-year-old children, and that MMRV versus MMR + V is associated with an increased risk of seizures during that interval. While febrile seizures are the most common neurologic adverse events following immunization with measles-containing vaccines, the risk is small — less than one febrile seizure per 1,000 injections. Other previous studies have not found any increased risk for fever or febrile seizures following either vaccine among 4- to 6-year-old children.

“This level of safety monitoring for vaccines can give the public confidence that vaccine surveillance is ongoing and that if a safety problem existed, it would be detected,” said Dr. Klein. “Our findings offer reassurance that adverse outcomes of measles-containing vaccines are extremely rare and unlikely, and that parents of 1-year-old children can choose MMR + V instead of MMRV vaccines to reduce the low risk of fever and febrile seizures.”

Other authors of the study include Edwin Lewis, MPH, Bruce Fireman, MA, and Roger Baxter, MD, Kaiser Permanente Vaccine Study Center, Oakland, California; Simon J. Hambidge, MD, PhD, Kaiser Permanente Colorado, Denver and Department of Ambulatory Care Services, Denver Health; Allison Naleway, PhD, The Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon;

Jennifer C. Nelson, PhD, Group Health Cooperative and the University of Washington, Seattle; Edward A. Belongia, MD, Group Health Cooperative and the University of Washington, Seattle; W. Katherine Yih, PhD, MPH, Harvard Pilgrim Health Care Institute, Boston; James D. Nordin, MD, MPH, HealthPartners Research Foundation, Minneapolis; Rulin C. Hechter, MD, PhD, Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California; and Eric Weintraub, MPH, Immunization Safety Office, Centers for Disease Control and Prevention, Atlanta.

About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research (DOR) conducts, publishes and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and the society at large. It seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 550-plus staff is working on more than 350 epidemiological and health services research projects. For more information, visit

About the Kaiser Permanente Vaccine Study Center
The Kaiser Permanente Vaccine Study Center (VSC) helps ensure that the nation’s vaccines are safe and effective by conducting research to advance scientific understanding of vaccines at all levels of development. In collaboration with DOR, the VSC coordinates clinical trials of new vaccines at Kaiser Permanente’s largest medical facilities in Northern California and other sites in the northwest, Hawaii and Colorado. VSC studies of new vaccines have led to licensing of vaccines to prevent diseases caused by Haemophilus influenza, pneumococcus, chickenpox, meningitis and flu.

About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America’s leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve approximately 9.5 million members in eight states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: