Flu shots during pregnancy help shield babies from severe illness, study finds

If you’re pregnant, getting your flu shot will help protect you and your baby from ending up in the hospital with a severe case of the flu, according to a new study published in JAMA Pediatrics.

Pediatricians from UPMC Children’s Hospital in Pittsburgh were part of the study, which found that flu shots during pregnancy reduced hospitalizations in babies younger than 6 months by about 40% and reduced emergency room visits by about 20%. That period of time is critical for infants, who are still too young to get flu shots themselves.

The greatest protection was for babies younger than 3 months old, whose risk of flu-associated hospitalizations or emergency room visits was reduced by half.

“People always think about old people and influenza, but among children, the highest rate of hospitalization for flu is kids under 6 months of age,” said Dr. John Williams, chief of pediatric infectious diseases at Children’s Hospital. “Every year in this country, the group of kids most frequently hospitalized for flu is babies under 6 months.”

Children’s was able to participate in the study, Williams said, because it is part of a network of seven children’s hospitals around the country funded by the Centers for Disease Control and Prevention to gather data on respiratory infections in kids.

“We were able to learn a lot about what causes respiratory infections in kids, and thousands of mothers and their babies consented to share their data with us about which mothers got flu shots and which babies got flu. It’s something we’ve been interested in for a long time,” he said.

Best practices

Though the new study shows a connection to reduced hospitalizations, doctors already have known that getting the flu shot while pregnant is safe and provides protection, according to Dr. Devon Ramaeker, AHN maternal fetal medicine division director.

Antibodies from the mother are pumped across the placenta into the fetus, giving it the tools to fight off disease even before birth.

“That’s something we have recommended for a very long time, to also protect the pregnant patient and the baby,” Ramaeker said. “This is more evidence that it is effective.”

Even for family members who aren’t the pregnant mom, getting vaccinated helps protect the baby, Williams said.

“Because these are contagious (illnesses), there is a cocoon effect,” he said. “If people around the baby are vaccinated … that also reduces the chance. But we know from studies of whooping cough and tetanus that the biggest piece is these antibodies from the mother.”

Vaccine uptake for moms

Vaccines — whether for covid-19, flu or the new 2023 vaccine for respiratory syncytial virus (RSV) — are safe and effective during pregnancy, Ramaeker emphasized. However, vaccine uptake is often low among pregnant patients.

“About half of pregnant individuals will choose to get a flu vaccine during pregnancy, but I think that’s declined even a little further,” she said.

Despite this, flu hits pregnant women hard. In the winter of 2022 in the U.S., according to Williams, of women aged 20 to 50 who were hospitalized with the flu, half were pregnant.

“Pregnant moms are always a little concerned about ‘can I take this pill, should I eat that food,’ but the flu vaccine, we’ve been using basically the same flu vaccine for almost 60 years,” Williams said. “It’s been given to hundreds of millions of people, and we absolutely know it is completely safe and effective.”

Side effects from vaccines, such as shoulder pain, don’t mean the vaccine is not working or that it “gave you the flu,” Ramaeker said.

“That is your body’s immune system working to make those really good antibodies that are going to protect themselves and the baby,” she said. “That is the normal response.”

The third trimester is the most effective time to get the vaccine, Williams said. It’s not too late to get the flu vaccine for this season, he added.

“Flu circulates in our area typically until April. There are three different flavors of flu that circulate , and all three are in the vaccine,” he said. “There’s still lots of time to have protection from flu. … The best time to get it is whenever you can get it.”