Women who receive mRNA COVID-19 vaccines have high levels of protection against serious infection in pregnancy.

That is according to the first large, real-world study of the effectiveness of mRNA COVID-19 vaccines during pregnancy. The report in the Journal of the American Medical Associate Network Open said that was especially the case when two initial doses and a booster were received.

Regenstrief Institute and Indiana University researchers and colleagues advised that it did not matter whether the shots were administered before or during pregnancy.

The large study was important because pregnant women were excluded from COVID-19 mRNA vaccine clinical trials, the authors noted. “That two doses plus a booster are known to be safe and demonstrate protection against severe disease in pregnant women is reassuring, given growing evidence of increased risk of poor maternal outcomes associated with COVID-19 infection during pregnancy,” stated study coauthor Brian Dixon, PhD, MPA, director of public health informatics for Regenstrief Institute and Indiana University Richard M. Fairbanks School of Public Health. “This strongly suggests that, along with other preventive measures that expectant mothers or women who are considering getting pregnant can take to promote a healthy pregnancy, getting vaccinated and boosted against COVID should be high on the list.”

Pointing out that expectant mothers are at high risk for severe COVID-19, the case-control study included 5,492 healthcare encounters sought by pregnant women. The researchers sought to evaluate the estimated effectiveness of mRNA vaccination against medically attended COVID-19 among that cohort during Delta and Omicron predominance.

The study was conducted from June 2021 to June 2022 in a network of 306 hospitals and 164 emergency department and urgent care (ED/UC) facilities across 10 of the United States.

The results indicated that among 4,517 eligible CLI-associated ED/UC encounters and 975 hospitalizations, 885 (19.6%) and 334 (34.3%) were SARS-CoV-2 positive, respectively.

“During Delta predominance, the estimated VE [vaccine effectiveness] against COVID-19–associated ED/UC encounters was 84% (95% CI, 69%-92%) for 2 doses within 14 to 149 days, 75% (95% CI, 5%-93%) for 2 doses 150 or more days prior, and 81% (95% CI, 30%-95%) for 3 doses 7 to 119 days prior,” according to the report, which added that “estimated VE against COVID-19-associated hospitalization was 99% (95% CI, 96%-100%), 96% (95% CI, 86%-99%), and 97% (95% CI, 79%-100%), respectively. During Omicron predominance, for ED/UC encounters, the estimated VE of 2 doses within 14 to 149 days, 2 doses 150 or more days, 3 doses within 7 to 119 days, and 3 doses 120 or more days prior was 3% (95% CI, 49%-37%), 42% (95% CI, –16%-72%), 79% (95% CI, 59%-89%), and –124% (95% CI, –414%-2%), respectively; for hospitalization, estimated VE was 86% (95% CI, 41%-97%), 64% (95% CI, –102%-93%), 86% (95% CI, 28%-97%), and –53% (95% CI, –1254%-83%), respectively.”

The researchers concluded that maternal mRNA COVID-19 vaccination, including booster doses, was associated with greater protection against medically attended COVID-19. “VE estimates were higher against COVID-19–associated hospitalization than ED/UC visits and lower against the Omicron variant than the Delta variant. Protection waned over time, particularly during Omicron predominance,” they added.

“This study indicates that pregnancy doesn’t diminish mRNA vaccine performance in protecting against severe COVID-19 despite immune differences between pregnant and nonpregnant women,” stated study coauthor Shaun Grannis, MD, MS, vice president for data and analytics at Regenstrief Institute, Regenstrief Professor of Medical Informatics, and professor of family medicine at Indiana University School of Medicine. “Vaccine utilization among expectant mothers remains low compared to similarly aged non-pregnant individuals for both the first two vaccines and a booster dose. Hopefully, this study will provide pregnant women with the evidence they need to get vaccinated and boosted.”

The CDC and the American College of Obstetricians and Gynecologists currently recommend that all pregnant women receive two vaccine doses and a booster dose, with a preference for mRNA vaccines.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

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