The impact of risk prioritization in COVID-19 vaccination in Belgium on hospital and intensive care unit admissions

Belgium prioritized primary COVID-19 vaccination of persons aged 18-64 years with underlying health conditions over their same-aged peers, leading to an accelerated administration of a first dose of 35 days. We assessed this strategy's impact on hospital admissions, in comparison to alternative scenarios, using generalized causal inference techniques with a hierarchical Bayesian model. A solely age-based scenario showed a significant increase in hospital admissions of 254, while random-allocation and no-vaccination scenarios showed even higher increases (604 and 1998, respectively). These results emphasize the importance of prioritization strategies in a pandemic context and the benefits of COVID-19 vaccines in general.