Background/aimsThe COVID-19 pandemic situation poses new challenges for research. Ethical issues might arise if especially vulnerable individuals for severe COVID-19 course expose themselves because of participation in studies to a higher risk of infection for study purposes. How is the feasibility and acceptance of self-organized blood sample collections to measure anti-SARS-CoV-2 Spike IgG antibodies in persons with a high risk for a severe COVID-19 disease progression?MethodsPersons with a high risk for a severe COVID-19 disease progression (immunocompromised, oncology patients or over 80 years old) were recruited between January and September 2021 to send in blood samples (at least 500 μl) 1 month and 6 months after second COVID-19 vaccination. Participants were given the choice of drawing capillary or venous blood themselves or having blood drawn by health professionals belonging to either the study’s own research team or the personnel found in local practices or clinics. Participants were surveyed via a telephone interview in December 2021 and January 2022 about their choice of blood sampling methods and influence of blood collection choice upon study participation.ResultsData from 360 participants was collected via telephone follow-up. First blood samples were collected by the participants themselves (35.8%), local practices or clinics (31.9%) and the research team (22.5%). Second blood samples were mostly collected in local practices or clinics (35.6%) followed by participants themselves (25.9%) and the research team (11.5%). Blood samples were not collected in 2.5% and 19.1% of persons during first and second blood draw, respectively. Only 2% of blood samples did not reach the laboratory or were not analyzable. About one-fourth (26%) of participants stated that they would not have participated in the study if it would have been required to travel to the university hospital to give their blood sample.ConclusionsParticipants were able to self-organize blood collection, making use of several different blood sample methods. Nearly all blood samples were analyzable when self-collected and sent in by post. One-fourth of the participants would not have participated in the study if required to give their blood sample in the study location.Trial registrationGerman Clinical Trial Registry,DRKS00021152.