Seroprevalence of SARS-CoV-2 Infection in Portugal in May-July 2020: Results of the First National Serological Survey (ISNCOVID-19)

• Autor(a) principal: Kislaya, Irina
• Data de Publicação: 2021
• Outros Autores: Gonçalves, Paulo, Barreto, Marta, de Sousa, Rita, Garcia, Ana Cristina, Matos, Rita, Guiomar, Raquel, Rodrigues, Ana Paula, ISNCOVID-19 Group, On behalf of
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: https://www.actamedicaportuguesa.com/revista/index.php/amp/article/view/15122
• topic: Antibodies; Viral; COVID-19; COVID-19 Testing; Immunoglobulin G; Immunoglobulin M; Portugal; SARS-CoV-2; Seroepidemiologic Studies; Anticorpos Antivirais; COVID-19; Estudos Seroepidemiológicos; Imunoglobulina G; Imunoglobulina M; Portugal; SARS-Cov-2; Testagem COVID-19

Introduction: The aim of this study was to estimate and describe the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific antibodies (immunoglobulin M and/or immunoglobulin G) in Portugal in May-July 2020.Material and Methods: A cross-sectional seroepidemiological survey was developed after the peak of the first epidemic wave on a sample of 2301 Portuguese residents, aged 1 year or older. Survey sample was selected using a two-stage stratified non-probability sampling design (quota sampling). SARS-CoV-2 immunoglobulin M and immunoglobulin G antibodies were measured in serum samples by enzyme-linked immunosorbent assay. Seroprevalence estimates of immunoglobulin M and/or immunoglobulin G and 95% confidence intervals were stratified by sex, age group, health region and education.Results: Overall, seroprevalence was 2.9% (95% confidence interval: 2.0% - 4.2%). Higher prevalence rates were observed in male (4.1%, 95% confidence interval: 2.6% - 6.6%) and those with secondary education (6.4%, 95% confidence interval: 3.2% - 12.5%). Differences in seroprevalence by age group and region were not statistically significant.Discussion: The estimated seroprevalence of SARS-CoV-2 was higher than the cumulative incidence reported by the National Surveillance System but far from necessary to reach herd immunity.Conclusion: Our results support limited extent of infection by SARS-CoV-2 in the study population possibly due to early lockdown measures implemented in Portugal and support the need to continue monitoring of SARS-CoV-2 seroprevalence in order to increase our knowledge about the evolution of the epidemic and to estimate the proportion of the susceptible population over time.