Impact of the COVID-19 pandemic on routine immunization coverage of children and teenagers in Ontario, Canada

Abstract

Objectives

To assess immunization coverage for routine vaccinations in children (aged 4–7 years) and teenagers (aged 14–17 years) during the COVID-19 pandemic compared to the pre-pandemic period, in Ontario, Canada.

Methods

Retrospective cohort study using primary care electronic medical records data from the University of Toronto Practice-Based Research Network database from January 2018 to June 2022. Monthly estimates of vaccine up-to-date (UTD) coverage (defined as 1 dose of tetanus, diphtheria, and acellular pertussis (Tdap)-containing and 1 dose of measles, mumps and rubella-containing vaccines received after the 4th birthday for children; and 1 dose of Tdap-containing vaccine received after the 14th birthday for teenagers) and time series regression analysis were used to compare changes in mean coverage before and during the pandemic. We also examined if changes in coverage estimates over time were associated with sociodemographic factors.

Results

30,010 children and 31,624 teenagers were included. Mean monthly UTD coverage for children decreased significantly from 48.7 % (SD 2.1) pre-pandemic (January 2018 – February 2020) to 44.3 % (SD 1.3) in mid-pandemic period (July 2020–June 2021), and remained significantly lower in later pandemic period (July 2021 – June 2022). Mean monthly UTD coverage for teenagers was 34.6 % (SD 0.9) pre-pandemic and decreased to 16.7 % (SD 0.6) in later pandemic period. When adjusted for baseline differences, teenagers from neighborhoods with higher income, lower proportions of racialized and newcomer populations and from rural areas experienced larger decreases in UTD coverage during the pandemic. No significant differences were found in UTD coverage among children across the various sociodemographic factors.

Conclusion

Significant declines in immunization coverage for children and teenagers in Ontario were still observed by June 2022, highlighting the need to further study the long-term impact of the pandemic and implement effective catch-up interventions to increase immunization coverage and prevent outbreaks of vaccine-preventable diseases.