Maternal Influenza Vaccination During Pregnancy Not Tied to Adverse Early Childhood Outcomes

By Lisa Rapaport

June 14, 2021

(Reuters Health) - Women who receive the influenza vaccination during pregnancy are no more likely than those who don't to have offspring with adverse health outcomes in early childhood, a new study suggests.

Researchers examined data on 28,255 children born at 37 weeks' gestation or later, including 10,227 (36.2%) whose mothers received seasonal influenza vaccination during pregnancy. The main goal of the study was to assess associations between maternal influenza vaccination and immune-related outcomes such as asthma or infections, non-immune outcomes such as neoplasms or sensory impairment, and nonspecific adverse outcomes such as emergency department visits and hospitalizations.

After a mean follow-up period of 3.6 years, there was no significant association between maternal influenza vaccination during pregnancy and any of these adverse childhood health outcomes, researchers report in JAMA.

"This study adds to what we know about longer-term safety of influenza vaccination during pregnancy, and can reassure pregnant individuals as well as their care providers," said senior study author Deshayne Fell of the School of Epidemiology and Public Health at the University of Ottawa and the CHEO Research Institute in Canada.

"This is important because in carefully-controlled clinical studies, influenza vaccination during pregnancy has been shown to protect pregnant people from getting the flu, but also protects newborn infants from getting the flu in the first several months of life," Fell said by email.

Although clinicians advise all pregnant women to receive a flu shot, many do not, Fell said. One reason many pregnant women opt not to receive this vaccination during pregnancy is concern about the safety, Fell added.

Despite the lack of previous research identifying specific safety issues or long-term risks of influenza vaccination during pregnancy, some pregnant women may just be very cautious about a wide variety of things during pregnancy, Fell said.

"Our motivation for doing this study was to evaluate long-term safety of flu vaccination during pregnancy to be able to provide evidence that can help inform decision-making by pregnant people, their care providers and by public health officials," Fell said.

One limitation of the study is that it relied on physician billing records as well as a database partially informed by patient self-report to identify women who received influenza vaccination during pregnancy.

However, the results should reassure pregnant women and clinicians of the safety of maternal influenza vaccination during pregnancy, said Dr. Manish Patel, team lead for the Influenza Prevention and Control Team in the Influenza Division at the U.S. Centers for Disease Control and Prevention in Atlanta and coauthor of an editorial accompanying the study.

"Influenza virus infection poses a risk for pregnant moms and their babies, and safe and effective vaccines are needed to protect both," Dr. Patel said by email.

Optimal protection against influenza requires annual vaccination with updated vaccines, and that is why mothers have to get vaccinated with each pregnancy, Dr. Patel added.

"Abundant data have demonstrated effectiveness and safety of maternal influenza vaccination, particularly against outcomes around infant birth and during the first months of life," Dr. Patel said. "Data from this current study add to that body of evidence and showed that maternal flu vaccination is not associated with longer term side effects in children."

SOURCE: and JAMA, online June 8, 2021.