Health Care Workers Cohort Study in the EuCARE Project (EuCARE-HCW)

"The baseline for enrolment into the study is defined by the occurrence of the first known immunization event, either natural infection or vaccination. The follow-up is planned to last 24 months with respect to this baseline. In subjects with natural infection, the viral variant must be determined for each prospective case by analysis of a nasopharyngeal swab obtained as soon as possible at diagnosis. For historical cases where the variant was not determined and a contemporary nasopharyngeal swab has not been stored, the viral variant may be inferred when a specific variant was dominating the geographic area according to official records available at local health agencies. However, the variant assignment will be labelled as putative, rather than proved.~HCWs can be enrolled in the category of:~(i) vaccination not followed by any later infection, (ii) infection followed by vaccination and (iii) vaccination followed by infection."