Seroprevalence of Anti-Sars-Cov-2 Antibodies in Colombia, 2020: A Population-Based Study (preprint)

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to cause very high morbidity and mortality throughout Latin American countries. However, few population-based seroprevalence surveys have been conducted to quantify attack rates and characterize drivers of transmission. Methods: We conducted a population-based cross-sectional study to assess the seroprevalence of antibodies against in ten cities in Colombia between September and December, 2020. The study involved multi-stage cluster sampling at each city. Participants provided a serum sample and answered a demographic and risk factor questionnaire. Prior infection by was ascertained using the SARS-CoV-2 Total (COV2T) Advia Centaur - Siemens chemiluminescence assay. Findings: A total of 17863 participants from 7075 households participated in the study. Seroprevalence varied substantially between cities, ranging from 21% (95%CI 16-25%) in Medellin to 78% (95%CI 65-91%) in Guapi. There were no differences in seroprevalence by sex, but seropositivity was lower in adults 60 years or older and higher in certain ethnic groups. There was substantial heterogeneity in seroprevalence within cities, driven to a large extent by a strong association between socio-economic stratum and seropositivity. Interpretation: Colombia has been one of the Latin American countries most affected by the COVID-19 pandemic. This study documented very high attack rates in several Colombian cities by the end of 2020 and identified key drivers of heterogeneities including ethnicity and socio-economic stratum. Few studies of seroprevalence of have been conducted in Latin America, and therefore this study contributes to the fundamental understanding of the pandemic in the region.