Objectives
Since the SARS-CoV-2 outbreak, new virus variants have developed. Variants of concerns (VoC) may require adaptations of current vaccines. We aim to identify optimal vaccination strategies for a COVID-19 vaccine adapted to a hypothetical (VoC) focusing on age-specific prioritization of a partially vaccinated population and initially limited vaccination doses.
Methods
A dynamic agent-based population model for Austria was extended to capture the impact of different variants. A hypothetical, new VoC affects the current pandemic. The parameters for the variant’s infectivity, virulence, susceptibility to the current vaccine and initial vaccination coverage when the VoC is detected were varied in 81 scenarios. Evaluated vaccination strategies are: 1) revaccination of the elderly with the VoC-vaccine, 2) vaccination of the unvaccinated with the VoC-vaccine, 3) VoC-vaccine and the current vaccine provided to the unvaccinated, and 4) VoC-vaccine to elderly and current vaccine to unvaccinated compared to 5) continuing with the current vaccine, only to minimize COVID-19-related hospitalizations and deaths. A time horizon of ten months was considered.
Results
Prioritization of vaccination depends strongly on combination of effectiveness of the current vaccine for the VoC, vaccination coverage and VoC infectivity, less on additional information on VoC severity. For example, at a 75% reduced effectiveness of the current vaccine for the VoC: Minimizing hospitalizations are achieved by selecting strategy 1 followed by 3 (1 followed by 2) considering increased VoC-infectivity of 0% or 33% (66%) independent of vaccination coverage. Assuming a 50% relative reduction of the effectiveness of the current vaccine for VoC, for example for 33% and 66% increased infectivity of the VoC, we would prefer strategy 1 followed by 2, strategies considering revaccinations with VoC vaccine would not be a preferred option focusing on hospitalizations.
Conclusions
Our study provides a flexible vaccination-decision basis. The current analysis identified no generally preferred strategy for VoC-adapted vaccines.