Reactogenicity, pregnancy outcomes, and SARS-CoV-2 infection following COVID-19 vaccination during pregnancy in Canada: A national prospective cohort study

Objective: To describe self-reported reactogenicity, pregnancy outcomes, and SARS-CoV-2 infection following COVID-19 vaccination during pregnancy.

Design: National, prospective cohort study.

Setting: Participants across Canada were enrolled from July 2021 until June 2022.

Population: Individuals pregnant during the COVID-19 pandemic, regardless of vaccination status, were included.

Methods: The Canadian COVID-19 Vaccine Registry for Pregnant and Lactating Individuals (COVERED) was advertised through traditional and social media. Surveys were administered at baseline, following each vaccine dose if vaccinated, pregnancy conclusion, and every two months for 14 months. Changes to pregnancy or vaccination status, SARS-CoV-2 infections, or significant health events were recorded.

Main outcome measures: Reactogenicity (local and systemic adverse events, and serious adverse events) within 1 week post-vaccination, pregnancy and neonatal outcomes, and subsequent SARS-CoV-2 infection.

Results: Among 2868 participants who received 1-2 doses of a COVID-19 vaccine during pregnancy, adverse events described included: headache (19.5-33.9%), nausea (4.8-13.8%), fever (2.7-10.2%), and myalgia (33.4-42.2%). Reactogenicity was highest after the 2nd dose of vaccine in pregnancy. Compared to 1660 unvaccinated participants, there were no statistically significant differences in adverse pregnancy or infant outcomes, aside from an increased risk of NICU admission ≥ 24 h among the unvaccinated group. During follow-up, there was a higher rate of participant-reported SARS-CoV-2 infection in the unvaccinated compared to the vaccinated group (18[47.4%] vs. 786[27.3%]).

Conclusions: Participant-reported reactogenicity was similar to reports from non-pregnant adults. There was no increase in adverse pregnancy and birth outcomes among vaccinated vs. unvaccinated participants and lower rates of SARS-CoV-2 infection were reported in vaccinated participants.

Tweetable abstract: No significant increase in adverse pregnancy or infant outcomes among vaccinated versus unvaccinated pregnant women in Canada.