The study was led by Saad B. Omer, MBBS, MPH, PhD, assistant professor global health, epidemiology and pediatrics, Emory’s Rollins School of Public Health and Emory University School of Medicine.
Omer and his colleagues used a large surveillance dataset from the Georgia Pregnancy Risk Assessment Monitoring System to analyze the relationship between receipt of inactivated influenza vaccine during any trimester of pregnancy by mothers of infants born between June 1, 2004 and September 30, 2006 and their baby being premature and small for gestational age. Researchers included 4,168 mother-baby pairs in the analysis.
The authors found that babies born during the influenza season from October through May and whose mothers were vaccinated against influenza during pregnancy were less likely to be premature compared with infants of unvaccinated mothers born in the same period with an adjusted odds ratio of 0.60.
Compared with newborns of unvaccinated women, babies of vaccinated mothers had lower risk of being small for gestational age during the period of widespread influenza activity but the researchers did not find a statistically significant effect on small for gestational age babies during the other periods (pre-influenza activity period, local and regional influenza activity periods).
“When faced with the decision to receive the influenza vaccine in pregnancy women often focus on perceived risks of the vaccine to the fetus and do not consider benefits,” says Omer.
“Influenza vaccine has been administered for decades to pregnant women and has a strong safety record. In this paper, for the first time, we document a protective effect of the vaccine on the fetus and the newborn.”
Omer says this research only shows an association between influenza vaccination and reduced risk of prematurity, but does not demonstrate a causal link. He says studies in other populations, particularly randomized controlled trials, are needed to confirm their results.
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