The Impact of COVID-19 Vaccination on Mortality and Stringency Measures in Belgium: A Retrospective Analysis

Background Numerous studies have estimated the number of deaths averted by COVID-19 vaccination campaigns. However, many of these analyses assume static population behavior, overlooking the fact that, in the absence of vaccination, increased hospital burden would likely have triggered stricter transmission control measures and behavioral adaptations. Methods We used an age-structured, compartmental stochastic model calibrated to Belgian hospital data, incorporating various vaccination statuses, to simulate counterfactual transmission scenarios without vaccination. These simulations explicitly account for plausible behavioral changes and additional non-pharmaceutical interventions that would have been required to preserve healthcare system capacity. Results Our findings highlight the critical role of vaccination in mitigating mortality and hospital burden, even after accounting for behavior adjustments, particularly during the Delta variant wave. In the absence of vaccination, stringent and prolonged social restrictions would have been necessary, including lockdowns lasting at least two additional years. Sensitivity analyses reveal that the timing and intensity of such restrictions significantly influence infection dynamics and the duration of healthcare system strain. Conclusions Beyond reducing mortality and morbidity, Belgium’s COVID-19 vaccination campaign averted at least two additional years of stringent mitigation measures that would have been required to safeguard the healthcare system.