This is a summary, written by members of the CITF Secretariat, of:

McClymont E, Atkinson A, Albert A, Av-Gay G, Andrade J, Barrett J, Bogler T, Boucoiran I, Castillo E, D’Souza R, El-Chaâr D, Fadel S, Fell DB, Korchinski I, Kuret V, Ogilvie G, Poliquin V, Sadarangani M, Scott H, Snelgrove JW, Tunde-Byass M, Money D; COVERED Team. Reactogenicity, pregnancy outcomes, and SARS-CoV-2 infection following COVID-19 vaccination during pregnancy in Canada: A national prospective cohort study. Vaccine. 2023 Oct 19:S0264-410X(23)01215-X. doi:

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published in Vaccine, provides further reassurance that COVID-19 vaccination is effective and not harmful during pregnancy. Researchers reported that people – whether pregnant or not – had similar side effects from COVID-19 vaccines. Consistent with other studies, those vaccinated during pregnancy did not experience higher rates of adverse pregnancy or infant outcomes. This study was first authored by Dr. E. McClymont for a study group led by Dr. Deborah Money (University of British Columbia).

This study focused on the side effects, pregnancy outcomes, and the risk of SARS-CoV-2 infection following vaccination during pregnancy. It compared the outcomes between two groups: a vaccinated group, comprising people who received at least one vaccine dose during pregnancy but none before, and an unvaccinated group, who received no doses prior to or during pregnancy. It also compared side effects from COVID-19 vaccines experienced following vaccination during pregnancy with survey data from the general Canadian population.

Key findings:

  • Among 2,868 participants who received a COVID-19 vaccine (the majority received Pfizer-BioNTech) during pregnancy, self-reported side effects after one and two doses included: headache (19.5/33.9%), nausea (4.8/13.8%), fever (2.7/10.2%), and myalgia (33.4/42.2%).
  • Overall, self-reported side effects were similar between pregnant people and the general population. Injection site reactions and headache and nausea were more frequent in pregnant people while new health events were lower.
  • Among pregnant people, side effects (reactogenicity) were highest:
    • After the second dose of vaccine, compared to the first and third dose.
    • Following the Moderna vaccine, compared to the Pfizer-BioNTech vaccine.
  • Overall, there were no differences in adverse pregnancy and infant outcomes between those who were vaccinated and those who were not. However, there was a significantly increased risk of neonatal intensive care unit (NICU) admission longer than 24 hours among infants born to unvaccinated mothers.
  • Pregnant individuals who received COVID-19 vaccines had lower rates of SARS-CoV-2 infection compared to unvaccinated pregnant individuals.

These findings provide reassurance about the effectiveness and safety of COVID-19 vaccination during pregnancy and can be a useful counselling tool with patients. This is important given the disproportionate burden of COVID-19 when acquired in pregnancy.

This study involved pregnant individuals across Canada enrolled between July 2021 and June 2022 in The Canadian COVID-19 Vaccine Registry for Pregnant and Lactating Individuals (COVERED). Surveys were conducted at baseline, following each vaccine dose if vaccinated, and at the end of pregnancy. Regular follow-up surveys were given every two months for 14 months to capture changes in pregnancy status, vaccination status, SARS-CoV-2 infection status, or significant health events. Further study is currently underway to evaluate responses to COVID-19 vaccines in pregnancy during the Fall/Winter 2023/24