Risks and safety of pandemic H1N1 influenza vaccine in pregnancy: exposure prevalence, preterm delivery, and specific birth defects.

Abstract

UNLABELLED:

We estimated exposure prevalence and studied potential risks for preterm delivery (PTD) and specific birth defects associated with exposure to the unadjuvanted pH1N1-containing vaccines in the 2009-2010 and 2010-2011 influenza seasons. We used data from 4 regional centers in the United States collected as part of the Slone Epidemiology Center's Birth Defects Study. For PTD, propensity score-adjusted time-varying hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for exposure anytime in pregnancy and for each trimester. For 41 specific major birth defects, propensity score-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated. Among 4191 subjects, there were 3104 mothers of malformed (cases) and 1087 mothers of nonmalformed (controls). Exposure prevalences among controls were 47% for the 2009-2010 season and 38% for the 2010-2011 season; prevalence varied by geographic region. Results for PTD differed between the two seasons, with risks above and below the null for the 2009-2010 and 2010-2011 seasons, respectively. For 41 specific birth defects, most adjusted ORs were close to 1.0. Three defects had adjusted ORs>2.0 and four had risks<0.5; however, 95% CIs for these were wide.

CONCLUSIONS:

Among women exposed to pH1N1 vaccine, we found a decreased risk for PTD in the 2010-2011 season; risk was increased in 2009-2010, particularly following exposure in the first trimester, though the decrease in gestational length was less than 2 days. For specific major defects, we found no meaningful evidence of increased risk for specific congenital malformations following pH1N1 influenza vaccinations in the 2009-2010 and 2010-2011 seasons.

• Authors: Carol Louik, Katherine Ahrens, Stephen Kerr, Junhee Pyo, Christina Chambers, Kenneth L Jones, Michael Schatz, Allen A Mitchell
• Journal: Vaccine (Vaccine) Vol. 31 Issue 44 Pg. 5033-40 (Oct 17 2013) ISSN: 1873-2518 [Electronic] Netherlands
• PMID: 24016804 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)
• Copyright: Copyright © 2013 Elsevier Ltd. All rights reserved.

Chemical References

• Influenza Vaccines

Topics

• Adult
• Case-Control Studies
• Congenital Abnormalities (epidemiology)
• Epidemiological Monitoring
• Female
• Humans
• Influenza A Virus, H1N1 Subtype
• Influenza Vaccines (administration & dosage, adverse effects)
• Influenza, Human (prevention & control)
• Pregnancy
• Pregnancy Trimesters
• Premature Birth (epidemiology)
• Prevalence
• Risk
• United States
• Young Adult