Human Vaccines & Immunotherapeutics (Aug 2023)

Temporal trends and determinants of COVID-19 vaccine series initiation after recent pregnancy

  • Eszter Török,
  • Tavleen Dhinsa,
  • Sheryll Dimanlig-Cruz,
  • Gillian D. Alton,
  • Ann E. Sprague,
  • Sandra I. Dunn,
  • Prakesh S. Shah,
  • Darine El-Chaâr,
  • Annette K. Regan,
  • Kumanan Wilson,
  • Sarah A. Buchan,
  • Jeffrey C. Kwong,
  • Siri E. Håberg,
  • Christopher A. Gravel,
  • Nannette Okun,
  • Mark C. Walker,
  • Shannon E. MacDonald,
  • Sarah E. Wilson,
  • Jon Barrett,
  • Deshayne B. Fell

DOI
https://doi.org/10.1080/21645515.2023.2215150
Journal volume & issue
Vol. 19, no. 2

Abstract

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During the rapid deployment of COVID-19 vaccines in 2021, safety concerns may have led some pregnant individuals to postpone vaccination until after giving birth. This study aimed to describe temporal patterns and factors associated with COVID-19 vaccine series initiation after recent pregnancy in Ontario, Canada. Using the provincial birth registry linked with the COVID-19 vaccine database, we identified all individuals who gave birth between January 1 and December 31, 2021, and had not yet been vaccinated by the end of pregnancy, and followed them to June 30, 2022 (follow-up ranged from 6 to 18 months). We used cumulative incidence curves to describe COVID-19 vaccine initiation after pregnancy and assessed associations with sociodemographic, pregnancy-related, and health behavioral factors using Cox proportional hazards regression to estimate adjusted hazard ratios (aHR) and 95% confidence intervals (CI). Among 137,198 individuals who gave birth in 2021, 87,376 (63.7%) remained unvaccinated at the end of pregnancy; of these, 65.0% initiated COVID-19 vaccination by June 30, 2022. Lower maternal age (<25 vs. 30–34 y aHR: 0.73, 95%CI: 0.70–0.77), smoking during pregnancy (vs. nonsmoking aHR: 0.68, 95%CI: 0.65–0.72), lower neighborhood income (lowest quintile vs. highest aHR: 0.79, 95%CI: 0.76–0.83), higher material deprivation (highest quintile vs. lowest aHR: 0.74, 95%CI: 0.70–0.79), and exclusive breastfeeding (vs. other feeding aHR: 0.81, 95%CI: 0.79–0.84) were associated with lower likelihood of vaccine initiation. Among unvaccinated individuals who gave birth in 2021, COVID-19 vaccine initiation after pregnancy reached 65% by June 30, 2022, suggesting persistent issues with vaccine hesitancy and/or access to vaccination in this population.

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