OBJECTIVE: To characterize maternal and infant outcomes for pregnant women who received live H1N1 influenza vaccine and had no reported adverse events.
METHODS: We identified Vaccine Adverse Event Reporting System reports, which described receipt of live H1N1 vaccine during pregnancy without an indication of an adverse event at the time of the report during October 2009 to June 2010. We reviewed the initial reports and obtained pregnancy outcome and infant data through 6 months of age from medical records. We reviewed the numbers and characteristics of pregnancy complications and infant outcomes including major birth defects and medically important infant conditions. Rates of spontaneous abortion, preterm birth, and major birth defects and their 95% confidence intervals were calculated.
RESULTS: The Vaccine Adverse Event Reporting System received 113 reports stating receipt of live H1N1 vaccine during pregnancy with no adverse events reported. We obtained follow-up maternal records on 95 of the 113 (84%) live H1N1 reports (40.2% were vaccinated in the first trimester) and found: 87 live births (two twin pregnancies) and no maternal deaths occurred. Number and rates of pregnancy-specific adverse events included: 10 (10.5%, 5.8–18.3) spontaneous abortions; four (4.7%, 1.8–11.4) preterm deliveries at 35–36 weeks of gestation; three (3.4%, 1.2–9.7) infants had one or more major birth defects noted at birth: one cleft palate, one cleft lip, and one microtia (underdeveloped or absent external ear). Seven neonates and infants were hospitalized for medically important conditions. One infant death occurred in a 2.5-month-old boy as a result of pertussis.
CONCLUSION: Rates of spontaneous abortion, preterm birth, and major birth defects in pregnant women who received live H1N1 vaccine were similar to or lower than published background rates. No concerning patterns of medical conditions in infants were identified.
LEVEL OF EVIDENCE: III
No concerning patterns of pregnancy complications or infant medical conditions occur among women who receive influenza A (H1N1) 2009 live attenuated monovalent vaccine inadvertently.
Immunization Safety Office, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, the Birth Defects Branch, Division of Birth Defects & Developmental Disabilities, National Center on Birth Defects & Developmental Disabilities, the Epidemic Intelligence Service, Epidemiology Workforce Branch, Office of Public Health Scientific Services, and the Women's Health and Fertility Branch, Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, and the Department of Pediatrics, Emory School of Medicine, Atlanta, Georgia; and the Office of Biostatistics and Epidemiology, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland.
Corresponding author: Pedro L. Moro, MD, MPH, Immunization Safety Office, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, 1600 Clifton Road, MS D26, Atlanta, GA 30333; e-mail: firstname.lastname@example.org.
Funded by the Centers for Disease Control and Prevention and the U.S. Food and Drug Administration.
The authors thank Drs. Dixie Snider, Sonja Rasmussen, Frank Destefano, and Emily Jane Woo and Ms. Nadine Shehab for their valuable comments and advice and Dr. David Kleinbaum for statistical and epidemiological advice. The authors also thank the Centers for Disease Control and Prevention's Immunization Safety Office staff, whose work allowed this activity to be conducted.
Presented in part at the 15th Annual Vaccine Research Conference, May 7–9, 2012, Baltimore, Maryland, and the 61st Annual Meeting of the American Society of Tropical Medicine and Hygiene, November 11–15, 2012, Atlanta, Georgia.
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention or the U.S. Food and Drug Administration.
Financial Disclosure The authors did not report any potential conflicts of interest.