60-day mortality and the role of SARS-CoV-2 in hospital admissions of immunocompromised patients during later Omicron period: a population-based study in Sweden.

Background: Real-world data on hospitalised SARS-CoV-2-positive patients are important for post-pandemic preventive measures.

Objectives: This study aims to explore 60-day mortality of immunocompromised patients hospitalised in later Omicron period, accounting for the relevance of COVID-19 for hospital care.

Methods: A retrospective population-based cohort study in Östergötland County, Sweden, included all adult patients with a positive SARS-CoV-2 PCR test within 3 weeks of hospital admission. Clinical data including functional level (combined assessment of frailty and performance status), and COVID-19's impact on hospital care were collected from medical records. An adjusted binary logistic regression model was applied for the main outcome of 60-day COVID-19-related mortality, with immunosuppression as the main exposure.

Results: 1128 hospitalised SARS-CoV-2-positive patients were included in the analysis whereof 12.9% were immunocompromised. Hospital admission due to COVID-19 was significantly more common among immunocompromised than non-immunocompromised (71.9% vs 49.5%), and 60-day COVID-19 mortality was 10.5% and 8.0% (p = 0.41), respectively. The median age of patients hospitalised due to COVID-19 was 78 years, with most having low/very low functional levels and ≥3 comorbidities. Adjusted for possible confounders, immunosuppression showed a significantly increased risk of 60-day COVID-19-related mortality (OR 2.41, 95% CI 1.06-5.47, p = 0.04).

Conclusion: A majority of COVID-19-related hospitalisations during later Omicron period in a high immunity population, involved people over 70 years with low/very low functional levels and multiple comorbidities. Immunocompromised patients had a 2.5 times higher risk of 60-day COVID-19-related mortality. These findings underscore the need for targeted preventive measures in vulnerable elderly and immunocompromised populations to mitigate COVID-19-related hospitalisations and deaths.