Rates of COVID-19-Associated Hospitalization in Immunocompromised Individuals in Omicron-era: A Population-Based Observational Study Using Surveillance Data in British Columbia, Canada

Background People with immune dysfunction have a higher risk for severe COVID-19 outcomes. Omicron variant is associated with a lower rate of hospitalization but higher vaccine escape. This population-based study quantifies COVID-19 hospitalization rate in the Omicron-dominant era among vaccinated people with immune dysfunction, identified as clinically extremely vulnerable (CEV) population before COVID-19 treatment was widely offered. Methods All COVID-19 cases were reported to the British Columbia Centre for Disease Control (BCCDC) between January 7, 2022 and March 14, 2022. Case and population hospitalization rates were estimated across CEV status, age groups and vaccination status. Cumulative rates of hospitalizations for the study period were also compared between CEV and non-CEV individuals matched by sex, age group, region, and vaccination characteristics. Findings A total of 5,591 COVID-19 reported cases and 1,153 hospitalizations among CEV individuals were included. A third vaccine dose with mRNA vaccine offered additional protection against severe illness in CEV individuals. Vaccinated CEV population still had a significantly higher breakthrough hospitalization rate compared with non-CEV individuals. Interpretation CEV population remains a higher risk group and may benefit from additional booster doses and pharmacotherapy. Funding BC Centre for Disease Control and Provincial Health Services Authority