[Comparative analysis of clinical characteristics, evolution and mortality of hospitalized patients with COVID-19 during the first and second wave of the pandemic (ECCOVID Study)].

Introduction: Clinical features and outcomes of SARSCoV-2 infections may change between different waves of the pandemic. The objective of this study was to compare clinical characteristics and outcomes between two cohorts of patients hospitalized for COVID-19 during the first and second waves in Argentina.

Methods: Multicenter and prospective registry of patients =18 years old with a confirmed diagnosis of COVID-19 admitted to 18 hospitals in Argentina during the first wave (March to October 2020) and second wave (March to July 2021) of the pandemic. Demographics, clinical characteristics, and outcomes of these patients were compared.

Results: A total of 1691 patients were included (first wave n = 809, second wave n = 882). Hospitalized patients during the second wave were older (median 53 years vs. 61 years, p < 0.001), had more comorbidities (71% vs. 77%, p=0.007) and required more supplemental oxygen at admission (21% vs 62%, p < 0.001). During hospitalization, patients of the second wave required more supplemental oxygen (49% vs. 85%, p < 0.001), invasive ventilation (12% vs. 22%, p < 0.001) and had higher 30- day mortality (11% vs. 26%, p < 0.001). Comparing only patients who required supplemental oxygen during hospitalization, 30-day mortality was 20% and 30% p < 0.001 for the first and second wave, respectively.

Conclusion: Compared to patients admitted during the first wave, patients admitted with SARS-CoV2 during the second wave in Argentina were more seriously ill and had a higher mortality.