Do maternal flu shots during pregnancy impact early health outcomes?

Expectant mothers are routinely given vaccines during pregnancy to provide protection before the infant can be given childhood vaccinations. The impact of the maternal vaccinations on other early health outcomes in the infant are little understood. A literature review published in Pediatrics looked at the current information.¹

Investigators used Embase, Medline, Scopus, Web of Science, and CINAHL Plus to find articles that met the inclusion criteria. Studies that were published in English and reported original data that included in utero exposure to influenza vaccines as well as health outcomes in children aged <5 years were used. Each study was assessed by 2 authors for eligibility, study design, setting, population, vaccines, outcomes, and results.

There were 3647 records assessed and 9 met the inclusion criteria. The studies were all carried out in high-income countries in either North America or Europe and the study period for all 9 occurred between 1980 and 2012. Five of the studies were retrospective cohort studies; 2 were prospective cohort studies; 1 used a case-control design; and 1 was a randomized control trial. Pandemic influenza vaccines were studied in 6 studies and the other 3 investigated seasonal influenza vaccines.

The outcomes included infectious disease, which included pneumonia, sepsis, otitis media, as well as other conditions; atopic, which included asthma; autoimmune which included Crohn disease, juvenile arthritis, celiac disease, as well as others; and neurodevelopmental conditions, which included epilepsy, intellectual disability, as well as sensory disorders.

Two of the studies examined indicated a lower risk of gastrointestinal infection, all-cause hospitalization, and upper respiratory tract infection after in utero exposure to a pandemic influenza vaccination. Other studies indicated a potential increase in the risk of sepsis, Sjögren syndrome, and asthma after in utero exposure to a pandemic influenza vaccination and a risk of autism spectrum disorder following in utero exposure to a seasonal influenza vaccination, but the links were not statistically significant following adjustment.

The researchers concluded that in the few studies analyzed that in utero exposure to an influenza vaccine was not linked to adverse outcomes in early childhood. However, they said that further researcher would be needed to provide a stronger base of evidence.

Reference

1. Foo DYP, Sarna M, Pereira G, Moore HC, Fell DB, Regan AK. Early childhood health outcomes following in utero exposure to influenza vaccines: a systematic review. Pediatrics. July 27, 2020. Epub ahead of print. doi:10.1542/peds.2020-0375