This is a retrospective study of COVID-19 (Coronavirus Disease 2019) at the Infectious
Diseases Unit of the University Hospital of Ioannina. Quantitative and qualitative
patient data are collected from the hospital medical records. Epidemiological, clinical
and laboratory parameters are recorded on 7 different time points (day: 1, 3, 5, 7, 9,
11, 15) concerning 793 variables of interest in an electronic (computerised) database.
Patients are also followed-up after 90 days from hospital discharge (number of visits of
follow-up depends on patient's health status) at the Post-COVID and Long-term effects of
coronavirus (long COVID) outpatient clinic of University Hospital of Ioannina. Data from
this outpatient clinic are also recorded in an electronic database (189 variables of
concern for each patient) The investigators collect data from COVID-19 hospitalized
patients in the Infectious Diseases Unit of the University Hospital of Ioannina, from
March 1st 2020 and ongoing. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)
infection was diagnosed by reverse real time transcription-polymerase chain reaction
(RT-PCR) test performed on nasopharyngeal swab specimens. Data are obtained
retrospectively using patients' medical records (hard copy and digital records). All
medical records are imported in a digital database anonymously with a personal identifier
code for each patient, as prespecified by study protocol.

All data are collected following the highest standards set by the respective European
Guidelines for Good Clinical and Laboratory Practice in Research Studies/Protocols and in
accordance with the Helsinki Declaration. All participants in the study receive a
personal identifier code and are kept anonymous. The epidemiological, clinical and
laboratory data are collected and stored without being linked to personal data of the
patients, but only to the personal identifier code. Biological samples are not collected.
The collected clinical and laboratory data are archived in electronic databases (793
variables of concern for each individual patient).