A Outline of the present work. We conducted two nationwide matched cohort studies in COVID-19 outpatients using data routinely collected by the Croatian Institute for Public Health (CIPH) (see Study outline for details). B Anonymized raw data was prepared by CIPH from several databases that it maintains. COVID-19 patients were identified based on positive polymerase chain reaction (PCR) or rapid antigen testing (RAT) performed at dedicated public testing points (ICD-10 code U07.1), or based on epidemiological/clinical criteria (ICD-10 code U07.2). Patients first diagnosed by PCR/RAT testing when seeking hospital assistance for any reason were excluded at this step (at the time of raw database set-up, there were 23959 such subjects recorded). Individual data were linked to databases on vaccination, deceased persons, hospitalizations and Central Heath Information System (see Study outline for details). Anonymized data were further “tidied-up” by exclusion of subjects younger than 16 years and those with missing/erroneous entries on key variables. Also, repeated COVID-19 episodes were excluded and cut-off date for index COVID-19 diagnosis was set at August 15, 2021, as to allow a sufficiently long (shortest) follow-up for outcomes to occur (until October 31, 2022) (see Study outline for details). Based on International Classification of Disease version 10 (ICD-10) code entries and Anatomical Therapeutic Chemical (ATC) code entries patients were classified into cohorts in respect to issuance of prescriptions and underlying morbidity. Detailed definitions of cohorts in Study 1 and Study 2 are listed in Table 1. See also Study outline.