Background: Since the start of the COVID-19 pandemic, novel SARS-CoV-2 variants of
concern have emerged, some of which have become largely dominant including the B.1.1.7
(alpha), the B.1.617 (delta) and more recently the B.1.1.529 (omicron). The clinical
implications of the different variants in unvaccinated and vaccinated persons are still
not adequately characterized. The detailed understanding of the interplay between the
variants, vaccine immune responses and disease severity is still scarce.

Study objectives:

Overall objectives are:

- to collect data and/or biological material from COVID-19 in-patients in a diverse
setting of 12 clinics in 11 countries and 4 continents

- to analyse the clinical course of COVID-19 in in-patients in relation to the viral
characteristics

- to analyse the clinical course of COVID-19 in in-patients in relation to vaccines
used and vaccination schedules

- to deliver recommendations for optimized clinical management and treatment with
special consideration to viral characteristics and to used vaccines

Specific objectives are:

- To describe the patterns of clinical symptoms, therapeutic interventions and
clinical outcome in patients hospitalized from 12 hospitals/clinics, in 11 countries
and 4 continents.

- To assess the impact of viral variants / viral sequences on the clinical outcome
measured as all-cause in-hospital mortality, non-invasive mechanical
ventilation/high-flow nasal oxygen, mechanical ventilation, admission to intensive
care unit, length of time in intensive care and overall length of hospitalization.

- To assess the impact of different vaccines and vaccination schedules on the clinical
outcome measured as all-cause in-hospital mortality, non-invasive mechanical
ventilation/high-flow nasal oxygen, mechanical ventilation, admission to intensive
care unit, length of time in intensive care and overall length of hospitalization.

- To assess the impact of viral variants / sequences in response to treatment
interventions and the associated clinical outcome

- To assess the impact of different vaccines and vaccination schedules in response to
treatment interventions and the associated clinical outcome

- To provide WP2 in EuCARE with biological material for further studies on viral
characteristics and associated immune responses

- To provide WP5 in EuCARE with data for further studies using artificial intelligence