Perspective from Jane Frederick, MD, FACOG

Press Release

Disclosures: The authors report no relevant financial disclosures.
November 03, 2021
2 min read

Better timing with flu vaccination campaigns could protect more pregnant women, babies

Perspective from Jane Frederick, MD, FACOG

Press Release

Disclosures: The authors report no relevant financial disclosures.
You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

A study in Brazil suggested that vaccinating women earlier in the influenza season could improve birth outcomes.

Expectant mothers who had not been vaccinated against influenza and were infected had higher rates of complications, the researchers said, putting their babies at risk during birth and later in life.

Seasonal influenza already was circulating in the weeks and months before the rollout of national influenza immunization campaigns in the semiarid state of Ceará, the researchers said. Influenza circulation begins there as early as mid-March and peaks 2 to 3 months earlier than in the south and southeast of the country, yet all of Brazil sticks to the same vaccination schedule.

“This misalignment was associated with seasonal patterns of premature birth, low birth weight and birth by cesarean,” Sean R. Moore, MD, a pediatric gastroenterologist at the University of Virginia Children’s Hospital, said in a university press release.

The observational descriptive study included children born to mothers with severe acute respiratory infections (SARI) during pregnancy (n = 61) and a control group of randomly selected mothers who did not have SARI during pregnancy (n = 122) in Ceará from 2013 to 2018.

The researchers found that 30 to 40 weeks after the peak of influenza season, the average birth weight fell by 40 g and premature birth rates increased from 10.7% to 15.5%.

Also, the 61 babies born to mothers with SARI had significantly lower birth weights (P = .02), were more likely to be premature (P = .03), experienced shorter gestation times (P < .01) and had lower Apgar scores 5 minutes after birth (P < .01) than the 122 children in the control group.

These trends repeated year after year, the researchers said. H1N1 was the predominant subtype during almost all the seasonal outbreaks between 2013 and 2018.

Children exposed to influenza and other infections in the womb are at significantly greater risk for neurocognitive, physical and educational problems later in life, according to the researchers, who concluded that earlier influenza vaccination campaigns in Brazil would better protect pregnant women and their babies.

Brazil’s influenza season typically begins in Ceará, the researchers continued, so improving the timing of vaccination campaigns there ultimately could benefit the entire country.

Sean R. Moore

“Brazil is a country with enviably high influenza vaccine uptake — greater than 80% in people at high risk for severe influenza. Our data suggest giving vaccines earlier in the year in Ceará would better protect women during pregnancy and reduce bad outcomes,” said Moore.

Currently, influenza vaccines are not recommended for infants aged younger than 6 months.

“When a mother chooses to receive the flu vaccine during pregnancy, she is giving an early gift to her baby,” Moore said. “Mom’s vaccine-acquired antibodies are shared with her fetus and persist to help protect her baby against influenza during the vulnerable first months of life.”

The researchers said their findings could improve lives in Brazil and send a message about the importance of timely vaccination to the rest of the world.

“This study confirms the importance of the flu vaccine for pregnant mothers,” Daniel Roshan, MD, FACOG, FACS, of NYU Langone Health, who was not involved in the study, told Healio.

Daniel Roshan

“Of course, timing of the vaccine is important, and it should be given prior to peak flu season,” Roshan continued, adding that current U.S. recommendations say it should be given in the fall and as soon as possible.

“I think the timing of early fall is good and does not need to change,” he said. “All pregnant women should be aware of the risk of flu in pregnancy and receive the vaccine.”


Filho JQ, et al. Emerg Infect Dis. 2021;doi:10.3201/eid2709.203791.