Major Finding: Receipt of any flu vaccination was significantly associated with higher infant birth weight (3,178 gram vs. 2,903 grams) and longer gestational age (38.3 weeks vs. 36.8 weeks; both P less than .0001).
Data Source: Preliminary analysis of 1,641 women delivering at Duke University Hospital during the 2009-2010 influenza season.
Disclosures: The study was funded by the 2010 American College of Obstetricians and Gynecologists/Merck & Co. Research Award on Immunization. Dr. Fortner and her colleagues reported no relevant financial disclosures.
CHICAGO – Influenza vaccination appears to improve neonatal outcomes, but coverage remains inadequate among pregnant women.
Among 1,641 evaluable women delivering at Duke University Medical Center, Durham, N.C., during the 2009-2010 influenza season, receipt of any flu vaccination was significantly associated with higher infant birth weight (3,178 g vs. 2,903 g) and longer gestational age (38.3 weeks vs. 36.8 weeks; both P values less than .0001).
Women who received at least one flu vaccine also were significantly less likely to require an antepartum visit or hospital admission than were those who did not (39% vs. 44%; P = .005).
“This information supports prior accumulating data that receipt of a flu vaccine improves not only maternal outcomes, but also birth outcomes,” Dr. Kimberly Fortner said at the meeting.
In all, 44% of women in the preliminary analysis received both vaccines in compliance with recommendations, far higher than historical influenza vaccination rates of 12%-34% and comparable to other reports from the season. Another 7% elected no vaccine at all, and 24% of the population had no documented receipt of vaccine in obstetrical records or other electronic medical records.
Uptake of seasonal influenza vaccine was 58% vs. 55% for the 2009 H1N1 influenza vaccine, which is unique among published prior literature. Even though rates were nearly equal, 24% of women elected to receive only one of the two recommended vaccines, resulting in inadequate coverage, said Dr. Fortner of the Translational Medicine Institute at Duke.
The researchers hypothesized that pregnant women may have had inappropriate or inadequate vaccination during the 2009-2010 flu season due to issues of vaccine distribution, sensationalism of the H1N1 influenza pandemic, and recommendations by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices that pregnant women receive both the seasonal and H1N1 influenza monovalent vaccines.
The earlier women went in for prenatal care, however, the more likely they were to receive a vaccine, she said.
Mean gestational age at first prenatal visit was significantly lower at 14.8 weeks among women who received the vaccine, compared with 18.6 weeks for women who did not receive any vaccine and 21.2 weeks for those with unknown vaccine status (P less than .0001).
Black women and those with public insurance or no insurance were significantly less likely to receive any vaccine.
In multivariate analysis that adjusted for maternal age, black race, less than a high school education, Medicaid or no insurance, and medical comorbidities, receipt of any influenza vaccine during that season was significantly associated with an estimated 133.7-g increase in birth weight (P = .0003).
The vaccine gives pregnant women a greater chance of having a heavier baby who is born closer to term.