A 12-year study of two measles-containing vaccines, published in Paediatrics, 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, 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 immunisation 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, Kaiser Permanente Colorado, Denver and Department of Ambulatory Care Services, Denver Health; Allison Naleway, The Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon, Jennifer C. Nelson, 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, MPH, Harvard Pilgrim Health Care Institute, Boston; James D. Nordin, MD, MPH, HealthPartners Research Foundation, Minneapolis; Rulin C. Hechter, MD, research and evaluation, Kaiser Permanente Southern California, Pasadena, California; and Eric Weintraub, MPH, Immunisation Safety Office, Centers for Disease Control and Prevention, Atlanta.
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.
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 licencing of vaccines to prevent diseases caused by Haemophilus influenza, pneumococcus, chickenpox, meningitis and flu.