Moms-to-be are always encouraged to get the flu shot for their health and the health of their baby. But what happens if you already got a flu shot months or a year ago? Would a new shot even do any good? New research says yes, flu shots for pregnant women—even those who recently got one—have major benefits for them and babies before they can receive their own vaccinations.

“As soon as we know you are pregnant, you should get a flu shot. The sooner the better,” said study co-author Dr. Octavio Ramilo, chief of the infectious diseases division at Nationwide Children's Hospital in Columbus, Ohio, in a new WebMD report.

This is because not only is influenza more serious among pregnant women, but the flu shot also serves to protect babies for months after their births.

In a press release this week, co-author Lisa Christian, associate professor and researcher from Ohio State’s Institute for Behavioral Medicine Research, explained they wanted to get to the bottom of the myth that pregnant women who had gotten a flu shot in the past year don’t need another.

“We launched this study to not only track how prior vaccination affects immune responses in expectant mothers,” she said. “But also to see whether it affects how well antibodies against the flu are transferred from the mother to the baby.”

Previous studies suggested the flu shot was the best way to protect moms and babies—but they also showed people who get a flu shot annually will gradually have lower antibody responses. That made experts wonder whether the infants of moms who got the flu shot every year we're getting enough of those flu fighting antibodies.

Thanks to the new study, we now have more evidence that pregnant women should make getting a flu shot one of their top priorities.

Christian’s team gave the shot to 141 pregnant women. Ninety-one of the women had received a flu shot in the previous year and 50 of them had not. For the moms, the results echoed those found in previous studies of adults: The women who’d had the shot the year before did have weakened antibody responses. But it was a different story for the babies.

“The good news is that we found that the benefits of maternal vaccination for the baby were not affected by prior vaccination in the mothers,” said Christian, whose team tested blood from babies’ umbilical cords. That is especially important as babies can’t get their own shots until they’re six months old, the antibodies we pass down are incredibly important.

In other words, expectant mothers who believed the flu shot wasn’t beneficial enough to justify getting one for their sakes should still get one for their baby’s health.

In many communities, flu shots are available by late August or September and take two weeks to reach full efficacy. As flu season lasts through spring and the effectiveness of the flu vaccine may wear off for people with lower immune systems, talk to your health care provider about whether you should get a booster shot later in the year.