While general advice is that those who are pregnant should receive a COVID-19 vaccine, because this patient group was excluded from the clinical trials, uncertainty remained over the safety of the vaccine.
Understanding the safety and efficacy of COVID-19 vaccines in those who are pregnant is vital to inform professional recommendations on maternal vaccination programmes. This is especially relevant given that some data indicates that infection with the virus in those who are pregnant leads to worse outcomes and are more likely to deliver preterm and there is even a potential increased risk of maternal death. As a result, a team from the Centres for Disease Control (CDC) v-safe pregnancy register, analysed the safety of vaccination among those who were pregnant. The v-safe is a CDC smartphone-based surveillance system in which those who register are sent links to surveys to assess and report adverse outcomes from vaccination and their health status post-vaccination. To identify those who received vaccination while pregnant or who became pregnant after vaccination, specific questions were included in the surveys. Individuals who have declared that they are pregnant and contacted and enrolled in the v-safe pregnancy program if they were vaccinated whilst pregnant. The v-safe team also used vaccine adverse event reporting system (VEARS) to characterise the safety of vaccines in pregnant women.
Between December 2020 and February 2021, 35,691 v-safe participants were identified as pregnant and who had received either the Pfizer-BioNTech or Moderna vaccine. Overall, 86.5% were pregnant at the time of vaccination with the remainder reporting becoming pregnant after vaccination. Among 3958 women enrolled in the v-safe pregnancy register, 827 had a completed pregnancy of which 115 (13.9%) lost their infant. Adverse outcomes for the newborn included preterm birth (9.4%) and a small size for gestational age (3.2%). An analysis of the VEARS data showed 221 reports involving pregnant women, the most frequent adverse event was spontaneous abortion in 46 cases.
The authors noted that there were no obvious safety signals among those who were pregnant at the time of vaccination, the level of adverse outcomes was no different to the published incidence prior to the pandemic. The authors concluded that while their data represented preliminary findings that required more longitudinal follow-up, it should help inform the vaccination decision-making process among those who are pregnant.
Shimabukuro TT et al. Preliminary Findings of mRNA Covid-19 Vaccine Safety in Pregnant Persons. N Engl J Med 2021