Study protocol for the SeMaCo study: A longitudinal regional cohort study to assess COVID-19 seroprevalence in blood donors

Introduction : Serologic studies are crucial for clarifying the regional dynamics of the SARS-CoV-2 coronavirus pandemic as well as the success of a vaccination campaign against COVID-19. We describe a cohort study investigating the seroprevalence of antibodies against SARS-CoV-2 in Magdeburg (Saxony-Anhalt, Germany). Protocol and study design : The SeMaCo study (Serologische Untersuchungen bei Blutspendern des Grosraums Magdeburg auf Antikorper gegen SARS-CoV-2) is a longitudinal, regional cohort study to assess the seroprevalence of COVID-19 in blood donors from Magdeburg (Capital of Saxony-Anhalt) and surrounding areas. We consider blood donors as a surrogate for the healthy, working-age population of Saxony-Anhalt. The study primarily aims to measure the prevalence and kinetics of IgG antibodies against SARS-CoV-2 in first time and repeat blood donors over a period of 21 months. The study explores four survey periods of three to four months each (January–April 21, July–October 21, February–April 22, July–October 22). At each visit, we will assess the attitude towards vaccination, the antibody response following vaccination, as well as undesired vaccination effects. Furthermore, we will collect data on occupational activities, housing conditions and the frequency of family and other social contacts. Discussion : The SeMaCo study extends the spectrum of seroepidemiological investigations in Germany. A longitudinal observation with repeated testing and serial interviews can provide a more accurate view on the dynamics of COVID-19 prevalence and spread than repeated cross-sectional studies. Based on interim results from similar studies, we expect a seroprevalence of SARS-CoV-2 antibodies below 5% in the first survey period. SeMaCo will influence policy decisions and preventative measures.