The aim of this study is to apply serology testing methods for SARS-CoV2 antibodies in samples collected from HCWs in an acute hospital. This will enable the identification of those who are protected and non-infectious for SARS-CoV2 and those who are seronegative and therefore potentially susceptible and infectious on patient contact. Prospective testing will provide data on the acquisition of SARS-CoV2 infections among HCWs and associated risk factors for transmission during a pandemic at an acute care hospital facility in the capital region of Denmark.

Hypothesis: Serial seroconversion measurements in hospital employees improve the organization of the clinical treatment and care during the COVID-19 pandemic at Nordsjællands Hospital and Nykøbing Falster County Hospital.

The study is a prospective cohort study. Weekly (in the first phase) and bi-weekly (in the second phase) serum samples will be drawn and shipped bi-weekly to laboratory collaborators in United Kingdom for antibody analyses during the course of the local epidemic, expected to last 10-12 weeks or more. After the cease of the epidemic serum will be drawn in 3-monthly intervals in a smaller group of seroconverted volunteers to follow the long-lasting immunity of SARS-CoV-2 infection up to 5 years post-pandemic.

Nurses, medical doctors, biomedical laboratory scientists, social health care assistants, and few healthcare administrators (as controls) will be invited for enrolment. In hospitals, all departments with staff that are in physical contact with patients during the pandemic will be invited to participate in the study.

Inclusion Criteria: hospital employee

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Exclusion Criteria: none

Health care workers at two Danish hospitals