July 25, 2019
1 min read

No link between flu vaccination in utero and child health problems

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Photo of Laura Walsh
Laura Walsh

There are no links between exposure to the 2009 pandemic H1N1 influenza vaccine during pregnancy and early childhood health problems, according to a recent study published in The BMJ.

“Our findings mean that health care providers can feel confident when recommending influenza vaccination to pregnant women,” Laura Walsh, MS, a data analyst at BORN Ontario and the study’s lead author, told Infectious Diseases in Children. “The results add to the already strong safety profile of flu shots during pregnancy and should help ease concerns by showing no negative health effects for children’s first 5 years of life.”

The study followed 104,249 Canadian children born from November 2009 through October 2010 until 5 years of age. According to the researchers, 30% of the population was exposed to the pH1N1 influenza vaccine in utero. They found no significant associations between vaccination and “upper or lower respiratory infections, otitis media, any infectious diseases, neoplasms, sensory disorders, urgent and inpatient health services use, pediatric complex chronic conditions, or mortality.”

pregnant woman recieving flu shot 
Source: Adobe Stock

A weak connection was discovered between in utero pH1N1 influenza vaccine exposure and a decreased risk for gastrointestinal infections (adjusted incidence rate ratio = 0.94; 95% CI, 0.91-0.98) and an increased risk for asthma (adjusted HR = 1.05; 95% CI, 1.02-1.09), but researchers believe these results can be attributed to residual confounding.

The study’s findings echo other reports that found no correlation between influenza vaccinations in pregnant mothers and health issues in their children, including a 2017 study that observed “no new or unexpected patterns in fetal or maternal outcomes” from 2010 to 2016.

“A large body of evidence supports the safety of influenza vaccination during pregnancy on newborn health, and this large population-based study extends this assessment to the child’s first 5 years of life,” Walsh said. “Further research is necessary to replicate these findings in different populations and with different influenza vaccines.” – by Eamon Dreisbach


Moro P, et al. Drug Saf. 2017;doi:10.1007/s40264-016-0482-1.

Walsh LK, et al. BMJ. 2019;doi:10.1136/bmj.l4151.

Disclosures: Walsh reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.