COVID-19 hospitalisations and all-cause mortality by risk group in Finland

Ever since COVID-19 was announced as a global pandemic in March 2020, healthcare systems around the world have struggled with the burden of the disease. Vaccinations and other preventive measures have decreased this burden, but severe forms of COVID-19 leading to hospitalizations and even deaths still effect certain risk groups, such as the elderly and patients with multiple comorbidities. The objective of this retrospective observational study was to identify which risk groups are at the highest risk for a severe COVID-19 infection in Finland using national registry data ranging from January 2021 to June 2022. The data was analysed in three time periods, enabling comparisons in high-risk groups between epidemiological waves caused by different variants of SARS-CoV-2. The summary level data were stratified according to predefined groups based on two criteria: age (>= 18 years, 18-59 years, and >= 60 years) and risk group. The results include analysis of infection hospitalisation rate (IHR), case fatality rate (CFR) and average length of stay (LOS) in both primary and specialty care for each risk group and age group. Our results confirm that despite the decrease in COVID-19 hospitalisations and deaths observed during the study period, a significant proportion of patients are still hospitalised, and deaths occur especially in the 60+ population. Also, even though the average length of stay of hospitalised COVID-19 patients has decreased, it is still long compared to specialty care hospitalisations in general. Old age is a significant risk factor for severe COVID-19 in all patient groups and certain risk factors such as chronic kidney disease clearly increase the risk for severe COVID-19 outcomes. Early treatment should be considered with a low threshold for risk group patients and for elderly patients in order to avoid severe disease courses, and to ease the burden on hospitals where resources are currently very strained.