Enrolment and sample collection
Thirty-four volunteers in East Tyrol with PCR-confirmed SARS-CoV-2 infections and mostly clinically manifested COVID-19 symptoms (31/34) were accompanied over 22 weeks post infection after informed consent was taken from the volunteers. Ethical approval of the study was obtained by the Ethics Committee of the University Hospital Wuerzburg no. 20201105_01.
Following the time range of initial data collection, we conducted serological follow-up examinations to evaluate possible recurrences and seroconversion rates. First blood draw occurred 21 – 43 days (median 35 days, standard deviation 15.6 days) after the onset of symptoms in the first week of April 2020, followed by further assessments during the investigative period, in the following called T1 – T4, and a final blood draw 5 and 6 months post infection in August and September 2020, respectively (T5). Clinical data were obtained using a standardised data collection form.
The presence of IgG-anti-spike1/spike2 and neutralizing antibodies was analyzed in follow-up serum samples by four different serologic methods to ensure validity of results: IgG in-house immunofluorescence assay (IFA), IgM in-house IFA, CLIA IGG® SARS-CoV-2 S1/S2 IgG (DiaSorin S.p.A., Saluggia, Italy) (CLIA IGG; clinical sensitivity 97.1%; 95% CI: 85.5 – 99.5%, clinical specificity 100%; 95% CI: 96.5 – 100% as reported by the manufacturer) and enzyme-linked neutralization assay (ELNA).