High vaccine coverage and non-pharmaceutical interventions decreased hospitalizations and deaths due to the Omicron variant in Newfoundland and Labrador, Canada

The Canadian province of Newfoundland and Labrador (NL) had high vaccination coverage, and few infections were reported prior to the establishment of the Omicron variant. We investigated whether changes in the timing and rate of booster dose administration could have reduced severe disease outcome and reliance on non-pharmaceutical interventions (NPIs) during the Omicron wave in NL. We used a vaccination-stratified epidemiological model calibrated to serology data to investigate the impact of vaccination relative to counterfactual vaccination strategies under actual, strict and no NPI scenarios. Compared with a Canadian vaccination rate scenario, the actual vaccination rollout in NL was estimated to have prevented approximately 519 hospitalizations and 122 deaths from December 15, 2021 to December 15, 2022, corresponding to reductions of 25.9\% and 30.9\%, respectively. These reductions reflected contributions from NL's higher initial primary series coverage (81.3\%), higher final booster dose coverage (57.3\%), and the implementation of various NPIs for 89 days after the Omicron BA.1 variant became established. Earlier and faster administration of booster doses reduced the duration of strict NPIs required to achieve hospitalization targets. Our findings show how the timing and rate of vaccination rollout can complement NPIs to reduce severe disease and the duration for which strict NPIs are required.