Is equitable priority vaccination of vulnerable people feasible in a real-world context? The case of Belgium.

Belgium has implemented a strategy to prioritize vaccination at population level during the COVID-19 pandemic, targeting individuals with pre-existing health conditions at increased risk of severe COVID-19. We aimed to evaluate whether prioritized groups were vaccinated sooner, and which socio-demographic and -economic characteristics were related to the speed of vaccine uptake. We calculated the time to vaccination between the start of the prioritization (1 April 2021) and receiving a first COVID-19 vaccine dose, using this interval as a proxy for evaluating the strategy's early impact. A multivariate regression model, incorporating priority status, age, sex, region of residence, income, and migration background, described the natural logarithm of this time gap. The sample included 4 472 873 individuals vaccinated between 1 April and 31 December 2021, of which 26.4% were prioritized. The results show a 34.6 days earlier vaccination for prioritized individuals versus non-prioritized ones. The time difference between the prioritized and non-prioritized groups was larger in the younger age groups compared to the older age groups (28.2 days versus 19.3 days). Based on the multivariate model estimates, being prioritized [βpriority = -0.37, 95% CI (-0.38; -0.36)], older age [β55-64 = -0.57, 95% CI(-0.58; -0.56)], residency in Brussels or Wallonia [βBrussels = -0.18, 95%CI (-0.20; -0.16); βWallonia = -0.18, 95% CI (-0.19; -0.17)], having a high income [βhigh income = -0.11, 95% CI (-0.12; -0.10)], being a Belgian national (βbelgian = reference), having had a recent prior infection (βno prior infection = reference) and being female (βfemale = reference) are associated with a shorter time to vaccination. Developing and implementing a prioritization vaccination strategy accelerated vaccination for the high-risk population with health conditions, demonstrating its feasibility in promoting equitable access to COVID-19 vaccines.