Inclusion Criteria:  Admitted to a Swedish ICU and registered in the Swedish intensive care registry with the ICD 10 diagnosis U07.1 before 1 July 2020. ICU-cohort.  or randomly selected from all patients admitted to hospital but not ICU with the ICD 10 diagnosis U07.1 in the national patient registry, matched on age, legal gender and region (four per ICU patient) before 1 July 2020. Hospital cohort.  or randomly selected from the general population (and not included in the ICU or hospital admitted cohorts), matched on age, legal gender and region (four per ICU patient)  Exclusion Criteria:  Missing a Swedish personal identification number