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

Sadarangani M, Soe P, Shulha HP, Valiquette L, Vanderkooi OG, Kellner JD, Muller MP, Top KA, Isenor JE, McGeer A, Irvine M, De Serres G, Marty K, Bettinger JA; Canadian Immunization Research Network. Safety of COVID-19 vaccines in pregnancy: a Canadian National Vaccine Safety (CANVAS) network cohort study. Lancet Infect Dis. 2022 Aug 11:S1473-3099(22)00426-1. doi: 10.1016/S1473-3099(22)00426-1

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 The Lancet Infectious Diseases, from the Canadian National Vaccine Safety (CANVAS) Network, led by Drs. Julie Bettinger and Manish Sadarangani (University of British Columbia/British Columbia Children’s Hospital Research Institute.

Key findings:

  • Among the vaccinated participants, reports of a significant health event A significant health event included any symptoms sufficient to cause work/school absenteeism, a medical consultation and/or prevent daily activities. within seven days of receiving a first dose of mRNA vaccine were slightly higher among those who were not pregnant (6.3%) than those who were pregnant (4%). The same applies after a second dose (non-pregnant: 11.3%; pregnant: 7.3%).
  • Among 339 unvaccinated pregnant participants, 3% reported similar health events as the vaccinated.
  • Comparing pregnant and non-pregnant vaccinated individuals, pregnancy was associated with decreased odds of a significant health event after any mRNA vaccine, whether for dose 1 or dose 2.
  • Pregnant participants had a 2.4 times increased odds ratio of having a significant health event after a second dose of any mRNA vaccine (primarily weighted by the high rate of significant health events post-Moderna vaccine which had an odds ratio of 4.4) compared to pregnant unvaccinated participants.
  • There was no difference in hospitalization or pregnancy-related complications between the pregnant individuals who have and have not been vaccinated.
  • Miscarriage was the most frequently reported adverse pregnancy outcome, and was more frequently reported by the unvaccinated (n=7, 2.1%) than the vaccinated (n=81, 1.5%). This suggests that vaccines did not increase the risk of pregnancy loss. Most miscarriages occurred in the 1st trimester of pregnancy.
  • Other adverse pregnancy outcomes, such as vaginal bleeding, abnormal fetal heart rate, and reduced fetal movement were rarely reported within seven days following any mRNA vaccination.

This study offers reassuring evidence that there is no significant association between vaccination status and significant health issues in pregnant people. It also highlights pregnant participants actually suffered fewer significant adverse events after vaccination than did similarly aged non-pregnant participants. The study was funded by CITF.

Researchers collected information from 191,360 vaccinated and 6,179 unvaccinated females of child-bearing age (15- 49-years old) from seven Canadian provinces and territories as of November 4, 2021. Among them, 5,597 were vaccinated and 339 unvaccinated participants were pregnant. This study collected data on significant and serious health events following immunization with the mRNA vaccines.