June 3, 2011

Flu vaccine during pregnancy may help reduce the risk of premature birth

Pregnant women who get flu vaccines may gain a protective edge to reduce the likelihood of premature births and low birth weight babies.

The recently-published study in PLoS Medicine on the effects of flu vaccine during pregnancy was led by Saad B. Omer, assistant professor global health, epidemiology and pediatrics in the Rollins School of Public Health and Emory School of Medicine.

Omer and his colleagues analyzed 4,168 mother-baby pairs and the effect of the influenza vaccine during any trimester of pregnancy by mothers of infants born between June 1, 2004 and Sept. 30, 2006.

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.

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. However, 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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