Evolving Mortality and Clinical Outcomes of Hospitalized Subjects During Successive COVID-19 Waves in Catalonia, Spain

Abstract

Background: The changes in shield strategies, treatments, emergence variants, and healthcare pathways might shift the profile and outcome of patients hospitalized with COVID-19 in successive waves of the outbreak. Methods: We retrospectively analysed the characteristics and in-hospital outcomes of all patients admitted with COVID-19 in eight university hospitals of Catalonia (North-East Spain) between Feb 28, 2020 and Feb 28, 2021. Using a mathematical model, we split admissions into four waves, one of them (summer wave) with little incidence. The main hospital outcomes included 30-day mortality and admission to intensive care unit (ICU). Findings: The analysis included 17,027 subjects admitted during the first wave (6,800; 39.9%), summer wave (1,807; 10.6%), second wave (3,804; 22.3%), and third wave (4,616; 27.1%). The highest 30-day mortality rate was reported during the first wave (17%) and decreased afterwards, remaining stable at 13% in the second and third waves (overall 30% reduction); the lowest mortality was reported during the summer wave (8%, 50% reduction). ICU admission became progressively more frequent during successive waves. In Cox regression analysis, the main independent predictors of 30-day mortality were the epidemic wave, followed by gender, age, diabetes, chronic kidney disease, and neoplasms. Interpretation: In-hospital COVID-19 mortality has decreased substantially after the first wave, but continues to be high and is highly dependent of patient’s characteristics and ICU availability. Highest mortality reductions occurred during a wave characterized by younger individuals, an increasingly frequent scenario as vaccination campaigns progress. Funding Information: This work was partially funded by the grant COVID19 6_17 (to Francesc Vidal), Direccio General de Recerca i Innovacio en Salut (Departament de Salut) and BIOCAT, Generalitat de Catalunya. Declaration of Interests: KK is a member of the UK Scientific Advisory Group for Emergencies. All other authors have nothing to declare. Ethics Approval Statement: The study protocol was approved by the independent ethics committee of the Hospital Germans Trias i Pujol (Badalona, Spain), which waived obtaining informed consent.