SAN FRANCISCO, CA—During a widespread period of influenza activity, white women and those of higher socioeconomic status who received an inactivated seasonal influenza vaccine while pregnant had significantly reduced odds of preterm births, while women enrolled in the Women, Infant and Child program and Black women had reduced odds of delivering children small for gestational age, a study that assessed racial and socioeconomic variations in vaccine effect reported at IDWeek 2013.

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“Maternal infections during pregnancy have been associated with adverse fetal and infant health outcomes, and vaccination against influenza is the most effective tool to prevent morbidity and mortality due to seasonal and pandemic influenza,” noted Saad Omer, PhD, MPH, MBBS, of the department of global health, epidemiology, and pediatrics, Emory University, Rollins School of Public Health, Atlanta, GA.

Dr. Omer and colleagues evaluated the association between receipt of the inactivated seasonal influenza vaccine on preterm and small for gestational age births.

The cohort study used data on 8,393 live births in Georgia from January 1, 2005, through December 31, 2008—the 4 most recent years available at study initiation—from the Georgia pregnancy risk assessment and monitoring system, hospital discharge data, and birth certificate data.

Among all women, we found significant strong associations between maternal influenza vaccination and reduced odds of a preterm birth during the widespread influenza activity period (OR 0.39; 95% CI 0.18–0.83],” Dr. Omer noted.

In stratified models, influenza vaccination was found to be protective against small for gestational age birth among women at higher risk for influenza-related morbidity during a widespread period of influenza activity. This included women enrolled in the Women, Infant and Child program (OR 0.20; 95% CI 0.04–0.98) and Black women (OR 0.15; 95% CI 0.02–0.94).

Maternal influenza vaccination was associated with reduced odds of a preterm birth among white women (OR 0.34; 95% CI 0.12–0.91) and women of higher socioeconomic status (OR 0.30; 95% CI: 0.12–0.74).

Dr. Omer noted, “Vaccination effects were stronger among women in higher risk categories.”