Long-term impact of the COVID-19 pandemic on childhood vaccination coverage in Quebec, Canada: A cohort study from the Canadian immunization research network

Objective: The COVID-19 pandemic disrupted routine childhood vaccination globally, increasing the risk of resurgences of vaccine-preventable diseases. This study assessed the long-term impact of the pandemic on vaccination coverage and timeliness for routine childhood immunizations for children born in 2017-2023. Methods: We conducted a retrospective cohort study in Quebec, Canada, using data from the Quebec Immunization Registry. We compared age-appropriate vaccination coverage by 3, 5, 13 and 19 months of age and the cumulative days undervaccinated during the first 24 months of life, from 2019 to 2023. Results: There was no decrease in vaccination coverage by 3 and 5 months of age in 2023 compared to 2019 for DTaP, Hepatitis B, rotavirus and pneumococcal conjugate vaccines. We observed a 0.8 percentage point decline (95% confidence intervals (CI):-1.2,-0.4) for ≥1 dose of the measles vaccine by 13 months of age, and a 1.0 percentage point decline (95%CI:-1.5,-0.06) for ≥2 doses by 19 months of age in 2023 compared to 2019. Overall, the mean number of days undervaccinated decreased across birth cohorts from 158.8 in 2019 to 133.8 in 2023. Conclusion: Delays in the administration of the measles vaccine remain concerning. Sustained efforts are needed to maintain high vaccination coverage and prevent outbreaks of vaccine-preventable diseases.