mRNA Covid-19 vaccine is safe in pregnancy

April 22, 2021

From Dec. 14, 2020 to Feb. 28, 2021, a research team used data from the “v-safe after vaccination health checker” surveillance system, the v-safe pregnancy registry, and the Vaccine Adverse Event Reporting System (VAERS) to characterize that mRNA Covid-19 vaccine is safe in pregnancy, according to an article released by The New England Journal of Medicine.

A total of 35,691 v-safe participants 16 to 54 years of age identified as pregnant. Injection-site pain was reported more frequently among pregnant persons than among nonpregnant women, whereas headache, myalgia, chills, and fever were reported less frequently. Among 3958 participants enrolled in the v-safe pregnancy registry, 827 had a completed pregnancy, of which 115 (13.9%) resulted in a pregnancy loss and 712 (86.1%) resulted in a live birth (mostly among participants with vaccination in the third trimester). Adverse neonatal outcomes included preterm birth (in 9.4%) and small size for gestational age (in 3.2%); no neonatal deaths were reported.

Although not directly comparable, calculated proportions of adverse pregnancy and neonatal outcomes in persons vaccinated against Covid-19 who had a completed pregnancy were similar to incidences reported in studies involving pregnant women that were conducted before the Covid-19 pandemic. Among 221 pregnancy-related adverse events reported to the VAERS, the most frequently reported event was spontaneous abortion (46 cases).

Preliminary findings did not show obvious safety signals among pregnant persons who received mRNA Covid-19 vaccines. However, more longitudinal follow-up, including follow-up of large numbers of women vaccinated earlier in pregnancy, is necessary to inform maternal, pregnancy, and infant outcomes.

The first coronavirus disease 2019 (COVID-19) vaccines available in the United States were messenger RNA (mRNA) vaccines: BNT162b2 (Pfizer–BioNTech) and mRNA-1273 (Moderna). In December 2020, the vaccines were granted Emergency Use Authorization (EUA) by the Food and Drug Administration (FDA) as a two-dose series, three weeks apart for Pfizer–BioNTech and one month apart for Moderna and were recommended for use by the Advisory Committee on Immunization Practices (ACIP). Pregnant persons were excluded from preauthorization clinical trials, and only limited human data on safety during pregnancy were available at the time of authorization. However, pregnant persons with COVID-19 are at increased risk for severe illness (e.g., resulting in admission to an intensive care unit, extracorporeal membrane oxygenation, or mechanical ventilation) and death, as compared with nonpregnant persons of reproductive age. Furthermore, pregnant persons with COVID-19 might be at increased risk for adverse pregnancy outcomes, such as preterm birth, as compared with pregnant persons without COVID-19. The Centers for Disease Control and Prevention (CDC) and ACIP, in collaboration with the American College of Obstetricians and Gynecologists and the American Academy of Pediatrics, have issued guidance indicating that Covid-19 vaccines should not be withheld from pregnant persons.

Post-authorization monitoring in pregnant persons is necessary to characterize the safety of these new COVID-19 vaccines, which use mRNA, lipid nanoparticles, and state-of-the-art manufacturing processes. Furthermore, establishing their safety profiles is critical to inform recommendations on maternal vaccination against COVID-19. We report preliminary findings of mRNA COVID-19 vaccine safety in pregnant persons from three U.S. vaccine safety monitoring systems: the “v-safe after vaccination health checker” surveillance system,10 the v-safe pregnancy registry, and the Vaccine Adverse Event Reporting System (VAERS).

The New England Journal of Medicine has the article.

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