Background

SARS-CoV-2 (=COVID19) has been a new challenge for health care systems around the world. Blood donation centers were also affected. At some point, vaccination against the virus was possible. In order to examine the prevalence of infections in vaccinated and non-vaccinated donors we performed a prospective observational, single-center study for antibodies against COVID19 ("wildtype" and "vaccination induced") from February until May 2022.

Methods

After their written informed consent participants were asked to complete a questionnaire about the number of vaccinations against SARS-CoV2 and any known COVID-19 infection. In addition, antibodies against the N-antigen ("nucleocapsid" of the wildtype virus) and the S-antigen ("spike antigen", vaccination induced) were detected via enzyme immune-essays (ECLIA-testing system, Cobas, Roche Diagnostics Mannheim). Laboratory results were compared with the provided information in the questionnaire with a special focus on unrecognized infections.

Results

2157 donors were tested between February and May 2022. 92% of them were vaccinated, 4% were not and 4% declined providing information on their vaccination status. Most of the donors (60-80%, depending on the number of vaccinations) were immunized by mRNA-vaccines such as Comirnaty or Spikevax (no matter whether it was the first, second, third, or the fourth vaccination). 398 donors were infected despite being fully vaccinated (18 %). These infections occurred mostly after at least 50 days after the last dose. There were no significant differences between the immunization schedules of the donors. 79 infections with SARS-CoV2 had been unrecognized and were only detected due to this study.

Conclusion

This single center study showed the success of vaccinations as well as the prevalence of seropositive donors from February until May 2022. By offering antibody testing, the blood donation center was able to address many first-time donors, so besides the study results, this study turned to a successful advertising campaign as well. Interestingly, approximately 24,7 % of infections with SARS-CoV2 had been unrecognized by the respective donor.

Offenlegung Interessenkonflikt:

The authors have no conflicts of interest to declare. All co-authors have seen and agree with the contents of the manuscript and there are no financial interests to report. We certify that the submission is an original work and is not under review at any other publication.