Reviewed by Zach Willis, MD, MPH; UNC Health, Chapel Hill, NC
Pregnant people are at increased risk of severe COVID-19 compared to non-pregnant women, but uptake of COVID-19 vaccines among pregnant people has been disappointing. Pregnant people were excluded from vaccine trials, and most studies to date have been uncontrolled. However, two recent studies directly address the safety of COVID-19 vaccination during pregnancy. Additionally, evidence is building that demonstrates that maternal vaccination also helps protect the infants as well.
Researchers in Israel analyzed pregnancy and neonatal outcomes for over 24,000 infants in a national health system covering approximately one quarter of the population; approximately two thirds were exposed to Pfizer-BioNtech vaccination in utero. After using inverse probability treatment weighting to balance the groups, they found no difference in the risk of preterm birth, small for gestational age (SGA), neonatal or post-neonatal hospitalization, congenital malformations or mortality. Similarly, a CDC study using Vaccine Safety Datalink data from eight healthcare organizations found no difference in preterm birth or SGA in over 40,000 pregnancies, of which 21.8% pregnant people received COVID-19 vaccine. In both large studies, vaccination of pregnant individuals was not associated with any adverse outcomes for the exposed infants, supporting the recommendation that all pregnant people be vaccinated according to the usual schedule.
Not only are vaccines safe and protective for pregnant individuals, there is now evidence of protection of their infants. Besides protecting the pregnant person during this high-risk period, infants of people vaccinated during pregnancy have protective antibodies against COVID-19. In a new study published in MMWR, researchers from 20 hospitals in 17 US states used a case-control approach to assess effectiveness of maternal vaccination on infants’ risk of COVID-19-related hospitalization. The study found that a 2-dose mRNA COVID-19 vaccination during pregnancy had a 61% vaccine efficacy in preventing COVID-19-related hospitalization during the infants’ first six months of life. It should be noted that the study was relatively small, with a total of 176 infants admitted due to COVID-19 matched to 203 infants hospitalized for other reasons, and the 95% confidence interval was relatively broad (31-78%).
The available evidence increasingly suggests that mRNA-based COVID-19 vaccination during pregnancy is: 1) safe for both the pregnant person and the developing fetus; 2) likely to protect the pregnant person during a high-risk period; and 3) likely to protect the vaccine-exposed infant via transplacental transfer of SARS-CoV-2-specific antibodies. Further study of these questions is needed in larger and diverse populations. Additionally, much remains to be learned in determining the optimal approach to vaccination during pregnancy, such as the use and timing of boosters. Public-health agencies should place a high priority on vaccination of pregnant individuals.
Goldshtein I, Steinberg DM, Kuint J, et al. Association of BNT162b2 COVID-19 Vaccination During Pregnancy With Neonatal and Early Infant Outcomes. JAMA Pediatrics. Published online February 10, 2022. doi:10.1001/jamapediatrics.2022.0001
Lipkind HS, Vazquez-Benitez G, DeSilva M, et al. Receipt of COVID-19 Vaccine During Pregnancy and Preterm or Small-for-Gestational-Age at Birth – Eight Integrated Health Care Organizations, United States, December 15, 2020-July 22, 2021. MMWR Morb Mortal Wkly Rep. 2022;71(1):26-30. doi:10.15585/mmwr.mm7101e1
Kashani-Ligumsky L, Lopian M, Cohen R, et al. Titers of SARS CoV-2 antibodies in cord blood of neonates whose mothers contracted SARS CoV-2 (COVID-19) during pregnancy and in those whose mothers were vaccinated with mRNA to SARS CoV-2 during pregnancy. J Perinatol. 2021;41(11):2621-2624. doi:10.1038/s41372-021-01216-1
Halasa NB, Olson SM, Staat MA, et al. Effectiveness of Maternal Vaccination with mRNA COVID-19 Vaccine During Pregnancy Against COVID-19-Associated Hospitalization in Infants Aged <6 Months – 17 States, July 2021-January 2022. MMWR Morb Mortal Wkly Rep. 2022;71(7):264-270. doi:10.15585/mmwr.mm7107e3