When Should Expecting Mothers Get a Flu Shot

A new study published today should help clarify an essential question for pregnant women considering getting an influenza vaccination during flu season, which generally begins in October each year in the United States.

An Original Investigation published by the journal JAMA Pediatrics on December 18, 2023, concluded that maternal vaccination was associated with reduced odds of influenza-associated hospitalizations and emergency department (ED) visits in infants younger than six months.

The vaccination effectiveness (VE) was most significant among infants younger than three months, for those born to mothers vaccinated during the third trimester, and against influenza-associated hospitalizations.

Furthermore, maternal VE increased with the severity of infant disease, reducing the risk in infants of ED visits by about 20% and reducing the risk of hospitalization by about 40%.

And maternal VE was higher in infants born to mothers vaccinated later during their pregnancy.

This prospective, test-negative case-control study used data from 2016 to 2017 through the 2019 to 2020 influenza seasons.

Overall vaccine effectiveness in infants was 34% (95% CI, 12 to 50), 39% (95% CI, 12 to 58) against influenza-associated hospitalizations, and 19% (95% CI, −24 to 48) against ED visits.

This study's findings indicate maternal influenza vaccination during pregnancy protects infants in the first few months of life before they are eligible for their own vaccination.

While continued efforts are needed to determine optimal timing, clinicians should continue to offer influenza vaccination at any time during pregnancy to protect both the pregnant person (women) and infant, wrote these researchers.

However, since there is limited, pregnant people (women) should talk to their healthcare provider about getting a flu shot for the best protection for themselves and their infants, they added.

According to recent U.S. Centers for Disease Control and Prevention (CDC) FLuView data, 14 influenza-associated pediatric deaths have already occurred during the 2023-2024 flu season. 

Last flu season, 182 influenza-associated pediatric deaths were reported.

In a separate Clinician Outreach and Communication Activity article, the CDC wrote that inactivated influenza vaccination during pregnancy is safe and effective and can protect young infants.

During the U.S. CDC vaccine committee meeting on October 25, 2023, Dr. Jamie Loehr (ACIP Work Group Chair) confirmed while there is considerable experience with the safe administration of influenza vaccines in pregnancy, there is less data specific to newer (cell-based) influenza vaccine formulations. 

The CDC wrote on December 18, 2023, that there's still time for expecting mothers to get vaccinated against the flu during the 2023-2024 flu season. Recent data indicates that over 152 million influenza vaccines have been distributed in the U.S. this flu season.