SARS-CoV-2, Tdap, and influenza vaccination during pregnancy from 2019 to 2022 in Ontario, Canada: a population-based retrospective cohort study

CMAJ. 2024 Sep 30;196(32):E1100-E1113. doi: 10.1503/cmaj.231522.

Abstract

Background: Hesitancy about vaccination during pregnancy posed challenges to SARS-CoV-2 vaccination efforts. We aimed to examine rates of SARS-CoV-2 vaccination among Ontario residents who gave birth in early 2022, and to compare rates of SARS-CoV-2 vaccine uptake with rates of tetanus, diphtheria, and pertussis (Tdap) and influenza vaccination during pregnancy in 2019, 2021, and 2022.

Methods: We conducted a population-based retrospective cohort study to describe vaccination rates among pregnant and comparable nonpregnant populations in Ontario using linked administrative data. Provincially insured females who had a live, in-hospital birth from Jan. 1 to Mar. 31 in 2019, 2021, or 2022 were our primary cohort. Using log-binomial regression, we tested associations between SARS-CoV-2 (2022) and Tdap and influenza (2019, 2021, 2022) vaccination status, with birth group and covariates. We compared SARS-CoV-2 vaccination status with the status of a matched cohort of nonpregnant females and conducted subgroup analyses by age and prenatal clinician type.

Results: Among birthing people, 78.7% received their first SARS-CoV-2 vaccine dose and 74.2% received a second dose. The rate was significantly higher among nonpregnant comparators (dose 1: relative risk [RR] 0.94, 95% confidence interval [CI] 0.93-0.94; dose 2: RR 0.91, 95% CI 0.90-0.91). However, the rate of SARS-CoV-2 vaccination uptake among birthing people was higher than uptake of Tdap or influenza vaccination. Tetanus, diphtheria, and pertussis vaccination increased over time from 22.2% in 2019 to 32.6% in 2022, and influenza vaccination rose to 35.3% in 2021 but returned to prepandemic levels in 2022 (27.7%). Vaccination rates were lower among pregnant people who were young, multiparous, or residents of rural or economically deprived areas for all 3 vaccines.

Interpretation: Rates of SARS-CoV-2 vaccination were lower among pregnant people than among nonpregnant comparators but were higher than rates of routinely recommended Tdap and influenza vaccinations. Pandemic urgency may have overcome a great deal of hesitancy about vaccinating against SARS-CoV-2 during pregnancy in 2022, but uptake of routinely recommended vaccines in pregnancy remains a challenge.

Trial registration: Clinicaltrials.gov, no. NCT05663762.

MeSH terms

  • Adult
  • COVID-19 Vaccines / administration & dosage
  • COVID-19* / epidemiology
  • COVID-19* / prevention & control
  • Diphtheria-Tetanus-acellular Pertussis Vaccines* / administration & dosage
  • Female
  • Humans
  • Influenza Vaccines* / administration & dosage
  • Influenza, Human* / epidemiology
  • Influenza, Human* / prevention & control
  • Ontario / epidemiology
  • Pregnancy
  • Pregnancy Complications, Infectious / epidemiology
  • Pregnancy Complications, Infectious / prevention & control
  • Retrospective Studies
  • SARS-CoV-2
  • Vaccination / statistics & numerical data
  • Young Adult

Substances

  • Influenza Vaccines
  • Diphtheria-Tetanus-acellular Pertussis Vaccines
  • COVID-19 Vaccines

Associated data

  • ClinicalTrials.gov/NCT05663762