Maternal Influenza Immunization and Reduced Likelihood of Prematurity and Small for Gestational Age Births: A Retrospective Cohort Study

• Type of Material: Article
• Authors: Saad B Omer, Emory University; David Goodman, Georgia Department of Community Health; Mark C. Steinhoff, Cincinnati Children's Hospital Medical Center; Roger Rochat, Emory University; Keith P Klugman, Emory University; Barbara J Stoll, Emory University; Usha Ramakrishnan, Emory University
• Language: English
• Date: 2011-05-31
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2011 Omer et al.
• License: Creative Commons Attribution 2.0 Generic
• Final Published Version (URL): http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1000441
• Title of Journal or Parent Work: PLoS Medicine
• ISSN: 1549-1277
• Volume: 8
• Issue: 5
• Start Page: e1000441
• End Page: e1000441
• Grant/Funding Information: The study was partially funded through the Emory University, Global Health Institute Faculty of Distinction Fund award (recipient: SBO).
• Research Categories: Health Sciences, Obstetrics and Gynecology; Health Sciences, Public Health

Abstract

Background: Infections during pregnancy have the potential to adversely impact birth outcomes. We evaluated the association between receipt of inactivated influenza vaccine during pregnancy and prematurity and small for gestational age (SGA) births. Methods and Findings: We conducted a cohort analysis of surveillance data from the Georgia (United States) Pregnancy Risk Assessment Monitoring System. Among 4,326 live births between 1 June 2004 and 30 September 2006, maternal influenza vaccine information was available for 4,168 (96.3%). The primary intervention evaluated in this study was receipt of influenza vaccine during any trimester of pregnancy. The main outcome measures were prematurity (gestational age at birth <37 wk) and SGA (birth weight <10th percentile for gestational age). Infants who were born during the putative influenza season (1 October–31 May) and whose mothers were vaccinated against influenza during pregnancy were less likely to be premature compared to infants of unvaccinated mothers born in the same period (adjusted odds ratio [OR] = 0.60; 95% CI, 0.38–0.94). The magnitude of association between maternal influenza vaccine receipt and reduced likelihood of prematurity increased during the period of at least local influenza activity (adjusted OR = 0.44; 95% CI, 0.26–0.73) and was greatest during the widespread influenza activity period (adjusted OR = 0.28; 95% CI, 0.11–0.74). Compared with newborns of unvaccinated women, newborns of vaccinated mothers had 69% lower odds of being SGA (adjusted OR = 0.31; 95% CI, 0.13–0.75) during the period of widespread influenza activity. The adjusted and unadjusted ORs were not significant for the pre-influenza activity period. Conclusions: This study demonstrates an association between immunization with the inactivated influenza vaccine during pregnancy and reduced likelihood of prematurity during local, regional, and widespread influenza activity periods. However, no associations were found for the pre-influenza activity period. Moreover, during the period of widespread influenza activity there was an association between maternal receipt of influenza vaccine and reduced likelihood of SGA birth.