Incidence and outcome of hospital-acquired COVID-19 infections in secondary and tertiary care hospitals in the era of COVID-19 vaccinations

Abstract

Abstract Objective: Hospital-acquired (HA) COVID-19 infections are known to increase morbidity and mortality. The aim of this study was to investigate the incidence and outcome of HA COVID-19 in different specialties across the wards in 18 hospitals belonging to the Helsinki University Hospital (HUH) responsible for secondary and tertiary care of a population of 1.8 million. Design: Retrospective population-based cohort study. Setting: Secondary and tertiary care hospitals. Patients: Inpatients with HA COVID-19 infection. Methods: The HA COVID-19 infections with patient characteristics were retrospectively searched from HUH patient database from 1st October 2021 to 31st March 2022. All positive SARS-CoV-2 nucleic acid amplification tests (NAATs) from any ward were reviewed. The COVID-19 infection was classified as HA if a notification of HA infection was done or SARS-CoV-2 NAAT was positive ≥6 days after hospital admission or medical records revealed a known exposure for COVID-19 during hospital stay. Results: 177 HA COVID-19 infections were retrieved with an incidence of 0.55 per 1000 patient days. Of these patients, 71 (40%) were treated in medicine, 52 (29%) in operative, and 54 (31%) in psychiatric wards, leading to incidences of 0.51, 0.39, and 1.10 per 1,000 patient days, respectively. In association with COVID-19, 16 (23%) in medicine, 3 (6%) in operative, and 1 (2%) patient in psychiatric wards deceased. Of the deceased patients, 16 (80%) had received at least one COVID-19 vaccine. Conclusions: Hospital-acquired COVID-19 infections in omicron era were related to high mortality, especially among patients in medicine wards who also had good vaccination coverage.