Flu Vaccine May Improve Birth Outcomes for Pregnant Women

Larry Hand

January 06, 2014

Pregnant women who receive the influenza vaccine during pregnancy may have lower odds of having a preterm delivery or delivery of a low-birth-weight baby compared with pregnant women who do not get vaccinated, according to a study published online January 6 in the Canadian Medical Association Journal.

Alexandra Legge, BSc, a fourth-year medical student at Dalhousie University, Halifax, Nova Scotia, Canada, and colleagues analyzed data from the Nova Scotia Atlee Perinatal Database for the 2 influenza seasons after the 2009 H1N1 pandemic. Of 12,223 women who gave birth to a live or stillborn baby between November 1, 2010, and March 31, 2012, only 1958 had received the influenza vaccine during pregnancy.

"The annual rate of seasonal influenza vaccination among pregnant women in Nova Scotia during the 2 nonpandemic influenza seasons immediately following the H1N1 pandemic was a disappointing 16%," the researchers write. That contrasts with a 64% rate of influenza-vaccinated pregnant women in Nova Scotia during the 2009 pandemic, but it is similar to vaccination rates preceding the pandemic, the researchers write.

Canadian and World Health Organizations guidelines recommend seasonal influenza vaccinations for pregnant women in any trimester. The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention (CDC) also recommends seasonal vaccination with the inactivated influenza vaccine for pregnant women.

In unadjusted analysis, the researchers found that vaccinated mothers had significantly lower odds of having a preterm (<37 weeks) birth (odds ratio [OR], 0.75; 95% confidence interval [CI], 0.60 - 0.93) or low-birth-weight (<5.5 lbs) child (OR, 0.71; 95% CI, 0.54 - 0.92). They found similar results after adjusting for potential confounders including maternal age, body mass index before pregnancy, smoking status, and infant's sex.

"Our findings add to the existing body of evidence that [show] that seasonal influenza vaccination during pregnancy not only offers maternal benefits, but may also provide both prenatal benefits to the fetus and postnatal protection to the infant through transplacental antibodies," the researchers write.

How to Improve Vaccination Rates

They offer this as a way to improve vaccination rates among pregnant women: "Thus far, the evidence suggests that rates are highest when pregnant women receive a recommendation for influenza vaccination from their antenatal care provider, who can then offer the vaccine in the same care setting."

Carolyn B. Bridges, MD, associate director for adult immunizations at the CDC in Atlanta, Georgia, agrees. The healthcare provider's recommendation is "the single most important predictor" for pregnant women getting vaccinated for influenza, she told Medscape Medical News. "Although it is best to have the vaccine available in the office, providers should still make the recommendation if they don't carry the vaccine."

Dr. Bridges cited recent CDC research findings that, in the United States during the 2012-2013 influenza season, vaccination coverage was 70.5% among surveyed US women who were pregnant at any time between October 2012 and January 2013 and who reported both a provider recommendation and an offer of vaccination. Coverage dropped to 46.3% if the women only received a recommendation but not an offer and plummeted to 16.1%, similar to the Canadian results, if they received no recommendation.

One coauthor reported receiving payment for attending a medical panel sponsored by Sanofi Pasteur and one coauthor reported having conducted clinical trials for manufacturers of influenza vaccines and receiving research funding from Sanofi and GlaxoSmithKline. The authors and Dr. Bridges have disclosed no relevant financial relationships.

CMAJ. Published online January 6, 2014.

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