Mom-to-Be's Flu Shot Doesn't Raise Autism Risk

TUESDAY, Sept. 1, 2020 (HealthDay News) -- Pregnant women are understandably worried about everything that goes into their bodies. But here's one worry they can cross off that list: flu shots.

A large, new study has confirmed that an expectant woman's flu shot doesn't increase the risk of autism in her child. And that's true even if the vaccine is given during the first trimester of pregnancy, the Swedish study found.

"The flu vaccine is safe during pregnancy. This study, as well as many others, have consistently shown that flu vaccine is safe," noted vaccine expert Dr. Paul Offit. He's director of the Vaccine Education Center at Children's Hospital of Philadelphia, and was not involved in the current research.

What can put mom and baby at risk is getting the flu.

"Pregnant women have a sevenfold increase of being hospitalized with pneumonia if they get the flu," Offit said. And women who get the flu during pregnancy also have an increased risk of delivering their baby early, according to the American College of Obstetricians and Gynecologists.

Autism spectrum disorders are developmental disorders that affect communication and behavior. Children with autism have varying degrees of impaired communication and social skills and they may engage in repetitive behaviors, the researchers said. These disorders are thought to stem from both hereditary and environmental factors.

The researchers -- led by Dr. Jonas Ludvigsson from the Karolinska Institute in Stockholm -- used data from national Swedish health registers. They looked at information on babies born between October 2009 and September 2010.

During that time, nearly 40,000 of infants were born to women who received a flu vaccine. The vaccine was specifically for the H1N1 (swine flu) strain. The children were compared to more than 29,000 infants whose mothers didn't get a vaccine.

After a follow-up of almost seven years, the researchers saw no significant difference in the rates of autism spectrum disorders among the children. Results were similar for flu vaccines given in the first trimester of pregnancy.

Ludvigsson said that research like this is even more critical right now. "Anticipating a vaccine against COVID-19, millions of pregnant women are likely to be offered such a vaccination. While our research group did not study COVID-19 vaccine effects, our research on H1N1 vaccination adds to the current knowledge about vaccines, pregnancy and offspring disease in general," he said in an institute statement.

The new study was published Aug. 31 in the Annals of Internal Medicine. Funding was provided by the Swedish Research Council and the Swedish Council for Working Life and Social Research.

Anders Hviid, a professor of pharmacoepidemiology from the Statens Serum Institut and University of Copenhagen in Denmark, said, "The current evidence supports that flu vaccines are safe to use in pregnancy and that they provide protection against a potential serious infectious disease for both mother and child." He wrote an editorial accompanying the study.

"This year, a flu shot will not only provide protection during pregnancy for mother and child and protection in early infancy due to transfer of maternal antibodies, but may also reduce the burden on our health care systems freeing up resources, if needed, during a possible autumn and winter COVID-19 resurgence," said Hviid.

He added that because of the potential benefits, it's "somewhat disheartening that influenza vaccination in pregnancy is not embraced to a greater degree."

Hviid said it's understandable to be concerned and vigilant during pregnancy. "I hope that the many studies supporting the safety of vaccines and their benefits can help overcome any reservations," he said.

Offit agreed that with the COVID-19 pandemic, it's even more important to get a flu vaccine.

"To protect themselves and their unborn child, pregnant women should get the flu shot," Offit advised, adding, "And get it as soon as possible."

More information

Learn more about flu vaccine during pregnancy from the American College of Obstetricians and Gynecologists.