Preliminary Findings of mRNA COVID-19 Vaccine Safety in Pregnant Persons

ABSTRACT

The first coronavirus disease (COVID-19) vaccines in the United States were the messenger RNA (mRNA) vaccines BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna). Pregnant persons were excluded from the original Emergency Use Authorization (EUA) issued by the Federal Drug Administration (FDA) in December 2020. Pregnant persons with COVID-19 are at increased risk for adverse pregnancy outcomes compared with pregnant persons without COVID-19. This study presents preliminary findings of mRNA COVID-19 vaccine safety in pregnant persons from the United States. To conduct this study, the researchers extracted data from 3 different US vaccine safety monitoring systems the "v-safe after vaccination health checker" surveillance system, the v-safe pregnancy registry, and the Vaccine Adverse Event Reporting System (VAERS). V-safe asks participants to report local and systemic signs and symptoms as mild, moderate, or severe during daily surveys. Women were eligible if they received their mRNA vaccination during pregnancy or during the preconception period, defined as 30 days before the last menstrual period through 14 days after, and were 18 years of age or older. Participant-reported pregnancy outcomes were spontaneous pregnancy loss (defined as spontaneous abortion and stillbirth) and neonatal outcomes (such as preterm birth, congenital anomalies, small size for gestational age, and neonatal death). Data were obtained through December 14, 2020, to February 28, 2021. In all, 35,691 v-safe participants ages 16 to 54 years identified themselves as pregnant. The majority of enrolled participants were between the ages of 25 and 44 years (98.8%), non-Hispanic White (79.0%), and did not report a COVID-19 diagnosis during pregnancy (97.6%). Overall, 92 (2.3%) of participants received their first vaccination dose during the preconception period, 1132 (28.6%) in the first trimester, 1714 (43.3%) in the second trimester, and 1019 (25.7%) in the third trimester. In terms of adverse effects, injection site pain was described more among pregnant persons compared with nonpregnant women. Headache, myalgia, chills, and fever were reported less often among pregnant persons compared with nonpregnant people. Of the 3958 participants enrolled in the v-safe pregnancy registry, 827 had a completed pregnancy. Of these, 827 completed pregnancies, 115 (13.9%) resulted in a pregnancy loss, and 712 (86.1%) resulted in a live birth (mainly 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. There were 221 pregnancy-related adverse events reported to VAERS, of which the most frequently reported event was spontaneous abortion (46 cases). No congenital anomalies were reported. Of note, the proportions of adverse pregnancy and neonatal outcomes in the v-safe pregnancy database were similar to those published before the COVID-19 pandemic. The findings from this study did not show obvious safety concerns among pregnant persons who received mRNA COVID-19 vaccines. More longitudinal follow-up and studies including larger numbers of women vaccinated earlier in pregnancy are needed to better inform outcomes. Further, new evidence has shown transplacental transfer of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies after maternal COVID-19 vaccination during the third trimester. This evidence suggests that maternal vaccination might provide some protection to the neonate. However, more data are needed to make evaluations on the level of protection.