Background: Since December 2019 the novel coronavirus (SARS-CoV-2) is the center of global attention due to its rapid transmission and toll on health care systems and global economy. Population-based serosurveys measuring antibodies for SARS-CoV-2 provide one method for estimating previous infection rates including the symptom-free courses of the disease and monitoring the progression of the epidemic.Methods: In June 2020 we succeeded in testing almost half of the population of an Austrian township (1,359 inhabitants) with a reported higher incidence for COVID-19 infections (17 PCR positive cases have been officially reported until the date of sample collection, i.e., 1.2% of the total population). We determined the prevalence of SARS-CoV-2-specific antibodies in this population, factors affecting, and symptoms correlated with prior infection. Antibodies were determined using a CE-certified quality-controlled ELISA test for SARS-CoV-2-specific IgG and IgA antibodies.Results: We found a high prevalence of 9% positive antibodies among the town population in comparison to 6% of the neighboring villages. This was considerably higher than the officially known RT-PCR-approved COVID-19 cases (1.2%) in the town population. Twenty percent of SARS-CoV-2-antibody positive cases declared being asymptomatic in a questionnaire. On the other hand, we identified six single major symptoms, including anosmia/ageusia, weight loss, anorexia, general debility, dyspnea, and fever, and especially their combination to be of high prognostic value for predicting SARS-CoV-2 infection in a patient.Conclusions: This population study demonstrated a high prevalence of antibodies to SARS-CoV-2 as a marker of past infections in an Austrian township. Several symptoms revealed a diagnostic value especially in combination.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic. The prevalence and persistence of antibodies following a peak SARS-CoV-2 infection provides insights into the potential for some level of population immunity. In June 2020 we succeeded in testing almost half of the population of an Austrian township with a higher incidence for COVID-19 infections. Now we performed a follow-up study to reassess the prevalence of SARS-CoV-2-specific IgA and IgG antibodies. In 121 people, including 68 participants of the previous study we found the prevalence of IgG and IgA antibodies remaining remarkably stable with 84% of our cohort prevailing SARS-CoV-2-specific antibodies, which is only a slight decrease from 93% four months before. Most patients with confirmed COVID-19 seroconvert, potentially providing immunity to reinfection. Our results suggest a stable antibody response that we observed for at least six months post infection with implications for developing strategies for testing and protecting the population.

Background: Since December 2019 the novel coronavirus (SARS-CoV-2) is the center of global attention due to its rapid transmission and toll on health care systems and global economy. Population-based serosurveys measuring antibodies for SARS-CoV-2 provide one method for estimating infection rates and monitoring the progression of the epidemic. Methods: In June 2020 we succeeded in testing almost half of the population of an Austrian township (n=835 of 1359 inhabitants) with a reported higher incidence for COVID-19 infections. We determined the level of prevalence for SARS-CoV-2 in this population, factors affecting, and symptoms correlated with prior infection. Results: We found a high prevalence of 9% positive antibodies among the town population in comparison to 6% of the neighboring villages. Only 20% of SARS-CoV-2 cases self-declared being asymptomatic. In contrast, we identified six single major symptoms, including anosmia/ageusia, weight loss, anorexia, general debility, dyspnea, and fever, and especially their combination to be of high prognostic value for predicting SARS-CoV-2 infection in a patient. Our comparison of the gold standard lab-based ELISA test and the on-site antibody test demonstrated a lack of accuracy for the latter test form. Conclusions: This population study demonstrated a high prevalence of antibodies to SARS-CoV-2 as a marker of both active and past infections in an Austrian township. Several symptoms revealed a diagnostic value especially in combination. Results from self-administered antibody tests should be considered with caution.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a global pandemic recently. The prevalence and persistence of antibodies following a peak SARS-CoV-2 infection provides insights into the potential for some level of population immunity. In June 2020, we succeeded in testing almost half of the population of an Austrian town with a higher incidence of COVID-19 infection. We performed a follow-up study to reassess the prevalence of SARS-CoV-2-specific IgA and IgG antibodies with 68 participants of the previous study. We found that the prevalence of IgG or IgA antibodies remained remarkably stable, with 84% of our cohort prevailing SARS-CoV-2-specific antibodies (only a slight decrease from 93% 4 months before). In most patients with confirmed COVID-19 seroconversion potentially provides immunity to reinfection. Our results suggest a stable antibody response observed for at least 6 months post-infection with implications for developing strategies for testing and protecting the population.