Effectiveness of the COVID-19 vaccines on preventing symptomatic SARS-CoV-2 infections and hospitalizations in Southwestern Alaska, January–December 2021

The population in rural southwest Alaska has been disproportionately affected by COVID-19. To assess the benefit of COVID-19 vaccines, we analyzed data from the regional health system. We estimated vaccine effectiveness (VE) during January 16–December 3, 2021, against symptomatic SARS-CoV-2 infection after a primary series or booster dose, and overall VE against hospitalization. VE of a primary series against symptomatic infection among adult residents was 91.3% (95% CI: 85.7, 95.2) during January 16–May 7, 2021, 50.3% (95% CI, 41.1%–58.8%) during July 17–September 24, and 37.0% (95% CI, 27.8–45.0) during September 25–December 3, 2021; VE of a booster dose during September 25–December 3, 2021, was 92.1% (95% CI: 87.2–95.2). During the overall study period, VE against hospitalization was 91.9% (95% CI: 85.4–95.5). COVID-19 vaccination offered strong protection against hospitalization and a booster dose restored protection against symptomatic infection.