The persistence of specific antibodies against SARS-CoV-2, the causative agent of COVID-19, is not yet fully understood. Using samples from individuals with antibodies (N = 353) from a prospective national serosurveillance study (Pienter corona Study) covering all ages, the breakdown into SARS-CoV-2 Spike specific IgM, IgA, and IgG antibodies were studied. S1 for a period of 7 months after infection and the effect of COVID-19-related symptoms on antibody levels. Also, they studied the development of avidity of anti-SARS-CoV-2 Spike S1 IgG antibodies as a marker of underlying cellular immunity and the functionality of the detected antibodies. Their data confirm that antibodies decrease rapidly, in the case of IgM and IgA isotypes. In contrast, 87% of the asymptomatic / mildly symptomatic participants and 95% of the symptomatic participants remained positive for IgG seven months after the onset of COVID-19 symptoms. Furthermore, the estimated 2-fold decrease in concentration over 158 days and the increasing avidity of IgG anti-Spike antibodies indicates the presence of memory B cells and/or long-lived plasma cells. Since IgG antibodies persist much longer than IgM and IgA antibodies, their detection provides better sensitivity for a long time after infection. Therefore IgG should be the isotype of choice in studies to assess the seroprevalence more than 2 months after infection and longitudinal studies. It is not yet known what antibody levels confer protection against reinfection or COVID-19 disease. The results help interpret the duration of immunity in unvaccinated individuals and provide a framework for evaluating vaccine-induced immunity to SARS-CoV-2.