Impact of the COVID-19 pandemic on routine vaccination coverage under varying prevalence Conditions: A cohort study in Beijing, China

Background: The COVID-19 pandemic has experienced various phases including outbreaks, a global health crisis, and eventual de-escalation from a public health emergency of international concern, significantly affecting the delivery and utilization of healthcare services. This study aimed to evaluate the impact of the COVID-19 pandemic on the coverage rate of routine immunization in children under varying prevalence conditions. Methods: We conducted a retrospective, population-based cohort study in Beijing, China, utilizing stratified random sampling by birthdate to obtain a sample of 29,811 participants. Subjects were categorized into four cohorts based on when they became eligible for vaccination: the Pre-COVID Period cohort, the COVID-19 Low Epidemic Period cohort, the COVID-19 Surging Period cohort, and the COVID-19 Slowing Down Period cohort. A one-month follow-up was conducted. Cox proportional hazards model was employed to examine associations between the COVID-19 epidemic status and timely vaccination. Results: Participants age-eligible for vaccination during the COVID-19 Low Epidemic Period demonstrated higher rates of timely vaccination (HR 1.18, 95% CI 1.15-1.22) compared to those eligible during the Pre-COVID Period. Conversely, those eligible during the COVID-19 Surging Period displayed lower rates (HR 0.73, 95% CI 0.66-0.82). No significant difference in vaccination timeliness was observed for those eligible during the COVID-19 Slowing Down Period in comparison to the Pre-COVID Period (HR 0.99, 95% CI 0.91-1.09). By the end of May 2023, DTP3 rate among eligible children during the COVID-19 Surging Period had surpassed 90%. Conclusions: Significantly declining rates of timely vaccination were observed during the COVID-19 Surging Period, which lasted two months, but not during the nearly three-year-long COVID-19 Low Epidemic Period. An upward trend in vaccination timeliness followed, culminating in a return to baseline levels over the subsequent 3-4 months. Our findings suggested that the pandemic exerted a decreasing and recoverable impact on the coverage rate of routine immunizations in China.