Salt Lake City—Vaccinating pregnant women against influenza appears to be a very beneficial two-for-one proposition.

A new study published in the journal Pediatrics finds that babies have a substantially reduced risk of contracting influenza during their first 6 months of life if their mother is vaccinated. That is in addition to the reduced risk of her getting the flu and suffering possible pregnancy complications, according to the report.

University of Utah School of Medicine researchers emphasize that getting more expectant mothers immunized should be a public health priority.

Infants 6 months and younger whose mothers were vaccinated when pregnant had a 70% reduction in laboratory-confirmed flu cases and an 80% reduction in flu-related hospitalizations compared with babies whose mothers weren’t immunized, according to the report.

Study authors point out that, according to health records, 97% of laboratory-confirmed influenza cases occur in infants of women who were not immunized against the disease while pregnant.

“Babies cannot be immunized during their first six months, so they must rely on others for protection from the flu during that time,” explained lead author Julie H. Shakib, DO, MS, MPH. “When pregnant women get the flu vaccine there are clear benefits for their infants.”

Co-author Michael W. Varner, MD, professor and vice chair for research in the Department of Obstetrics and Gynecology, adds that, while pregnant women are not at greater risk for getting the flu than other adults, they are more likely to be severely affected by the infectious disease.

For the study, the researchers reviewed more than 245,000 de-identified health records of pregnant women and more than 249,000 infant records, including multiple births, for nine flu seasons from December 2005 through March 2014. About 10% of the expectant mothers reported being vaccinated while pregnant, compared with 222,003 who said they were not vaccinated.

Among 658 infants identified with laboratory-confirmed influenza, 638 cases of the flu and nearly all of the hospitalizations—148 out of 151—occurred in babies whose mothers were not immunized, results indicate.

To confirm that the flu vaccine was the cause of the improved results, researchers also looked at respiratory syncytial virus rates in the infants, and found no difference between those who had been vaccinated and those who had not.

Although vaccination rates in pregnant women averaged 10% over the nine flu seasons studied, they increased significantly between June 2009 and September 2010, when the spread of the H1N1 flu reached pandemic levels worldwide, according to the report.

“This is a public health issue,” senior author Carrie L. Byington, MD, said in a University of Utah press release. “About 50 percent of pregnant women reported being immunized in the latest flu season. But we need to get that number much closer to 100 percent.”

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