Clinical Research Directory

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.