Influenza Vaccine During Pregnancy May Protect Newborn Infants

The number of expecting mothers who opt for annual vaccination for influenza during pregnancy remains relatively low; however, the results of a new study suggest this may be changing—and that there are obvious benefits for immunization for newborns.

According to research that will be published in June in the journal Pediatrics, the H1N1 influenza pandemic of 2009-2010 had a dramatic impact on the number of pregnant women who decided to receive vaccination against influenza. The authors of the study reviewed the maternal and infant records of nearly 250,000 births at Intermountain/University of Utah healthcare facilities over a 10-year period from 2005 through 2014.

Although, only approximately 10% of the mothers in the assessed patient population self-reported receiving influenza vaccine during their pregnancy over the course of the study period, there was a significant upward trend from the beginning of the study to the end, particularly following the H1N1 pandemic. The authors reported that while only 2.2% of mothers in the study self-reported receiving influenza vaccine in the early part of the study, that number increased to a high of 21.2% following the H1N1 pandemic.

“The public definitely became more aware of how much of a risk there was from influenza during the H1N1 pandemic,” study co-author Julie H. Shakib, DO, MS, MPH, assistant professor of pediatrics and medical director, Well Baby and Intermediate Nursery, University of Utah told Contagion. “This was also when many obstetric practices started delivering the vaccine as a routine part of care. Both of these factors have likely contributed to the sustained increase in influenza vaccination during pregnancy. Unfortunately, only half of pregnant women receive the flu vaccine during pregnancy [overall], so there is still more work to be done to improve these rates in pregnant women.”

Particularly since the benefits of vaccination for newborns are pronounced. According to Dr. Shakib and her colleagues, of the 658 infants in the study population born with laboratory-confirmed influenza, only 20 were born to mothers who self-reported receiving vaccination for influenza. Of 658 infants, 151 were hospitalized; however, only three of the hospitalized infants were born to mothers who self-reported receiving vaccination. Overall, the authors reported that infants born to women reporting influenza immunization during pregnancy had risk reductions of 64% for influenza-like illness, 70% for laboratory-confirmed influenza, and 81% for influenza hospitalizations in their first six months.

“No evidence exists [demonstrating] risk to the developing fetus from vaccinating pregnant women with the influenza vaccines,” noted Dr. Shakib. “Influenza vaccines are safe and important for pregnant women and their infants. Infants younger than six months are at the greatest risk of severe illness from influenza but are too young to be directly immunized. This is why vaccination during pregnancy is critical. Since infants younger than six months are too young to be vaccinated, the best way to protect them from influenza is to make sure their mothers receive the vaccine during pregnancy. Every medical provider directly involved in the care of pregnant women should both have the resources to provide and strongly advise their patients to get the influenza vaccine while they are pregnant.”

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.