Immune response to SARS-CoV-2 prior to vaccination among healthcare workers from Alto Paraná, Paraguay, a seroepidemiological study

Abstract

Background: Understanding the behavior of humoral response in COVID-19 continues to be a challenge to produce vaccines that provide long-lasting immunity. Aim: To describe the natural humoral response induced by SARS-CoV-2 among healthcare workers based on epidemiological and clinical profiles. Methods: Cross-sectional study in healthcare workers from public hospitals in the Department of Alto Paraná, Paraguay, 962 participants were recruited through consecutive sampling, using a questionnaire and blood sampling. Antibodies were determined by immunochromatography assay for detection of IgM and IgG and by SARS-CoV-2 IgG anti-spike capture ELISA method and factors associated with seropositivity were evaluated. Results: The overall seropositivity was 36.5% (95% CI: 33.4 – 39.5); 59.3% (n: 571) of respondents reported symptoms compatible with COVID-19 since the start of the pandemic and the date of blood draw, 44% (n: 251) of them tested positive; 10.4% (n: 100) who reported no history of symptoms tested positive. The factors associated with seropositivity were the presence of symptoms (p<0.0001); anosmia (p:0.011); to have a risk factor (p:0.036); working at the Presidente Franco District Hospital (p:0.016). No association with sociodemographic factors was observed. Seroprevalence in symptomatic participants varied according to the time elapsed from the onset of symptoms to serology: 34.3% (<15 days), 58.6 (15 - 90 days), 40.1% (>90 days). Conclusions: Clinical characteristics were mostly associated with seropositivity and seroprevalence in symptomatic participants varied according to the time elapsed from the onset of symptoms to serology.