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Vaccine Safety Datalink Study Finds Less Reaction To DTaP Vaccine When Given In Kids’ Thighs Than Arms

Children age 12 to 35 months who receive DTaP vaccine in their thigh muscle rather than their arm are around half as likely to be brought in for medical attention for an injection-site reaction. So says a new study of 1.4 million children at Group Health and seven other (VSD) centers across the country, e-published on January 14 in Pediatrics.

“These local reactions are the most common side effect of vaccinations,” said study leader , MD, MPH, a senior investigator at Group Health Research Institute. “But we have known relatively little about how to prevent them.” Local reactions go away after a day or two, but they can be painful, and the associated redness and swelling can concern parents. This study focused on “medically attended” local reactions: ones that resulted in a visit to a doctor, nurse, or emergency room. Ideally, medically attended local reactions would happen less often than the current nearly one in 100 vaccinated children.

“Our findings support current recommendations to give intramuscular vaccinations in the thigh for children younger than 3 years,” Dr. Jackson said. Since 2011, the (ACIP) has recommended that intramuscular vaccinations be given to toddlers aged 12 to 35 months preferably in the thigh muscle (or in the deltoid muscle of the arm only if it’s big enough) – and to children age 3 years older in the deltoid muscle of the arm. But in practice, health care providers tend to vary in their choice of vaccine injection sites for children; and parents can influence that decision.

The research team also tracked local reactions in children age 3 to 6 years and from intramuscular vaccines other than DTaP, including inactivated influenza and hepatitis A. But they found no statistically significant differences between vaccinating in the thigh and arm in the older age group or for the other intramuscular vaccines.

Previous evaluations of local reactions after the fifth DTaP vaccine in children age 4 to 6 years found that vaccination in the thigh was linked to a lower risk of local reactions than was vaccination in the arm. Dr. Jackson also led an earlier study that showed that neither ibuprofen (Advil) nor acetaminophen (Tylenol) help prevent local reactions after that vaccine.

The current research followed children age 1 to 6 years who received intramuscular vaccines from 2002 to 2009 at the eight VSD sites: Group Health; in Boston; HealthPartners in Minneapolis; Marshfield Clinic in Wisconsin; Colorado in Denver; Northwest in Portland; Northern California in Oakland; and Southern California in Los Angeles. The VSD project is a collaborative effort between the Centers for Disease Control and Prevention (CDC)’s Immunization Safety Office and 10 managed care organizations, including these eight (whose research institutes also happen to be members of the HMO Research Network).


This study was supported by the CDC (contract 200-2002-00732), through America’s Health Insurance Plans.

Dr. Jackson had five coauthors at Group Health Research Institute: Biostatistician Do Peterson, MS; Associate Investigator Jennifer C. Nelson, PhD; and Programmer Analysts Tracey Marsh, MS, and Lawrence Madziwa, MAS. Dr. Jackson also holds appointments at the University of Washington Schools of Public Health and Medicine. Her other coauthors were S. Michael Marcy, MD, of Kaiser Permanente Southern California’s Department of Research and Evaluation, in Pasadena; Allison L. Naleway, PhD, of Kaiser Permanente Northwest’s Center for Health Research, in Portland, OR; James D. Nordin, MD, MPH, of HealthPartners Institute for Education and Research, in Minneapolis; James G. Donahue, DVM, PhD, of , in Marshfield, WI; Simon J. Hambidge, MD, PhD, of Kaiser Permanente Colorado’s Institute for Health Research and Denver Health Community Health Services, in Denver; Carolyn Balsbaugh, MPH, of the Department of Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School, in Boston; Roger Baxter, MD, of the Kaiser Permanente Vaccine Study Center at the Division of Research in Oakland, CA; and Eric Weintraub, MPH, the CDC’s Immunization Safety Office, in Atlanta.

Group Health Research Institute