Álvarez-Antonio C, Meza-Sánchez G, Calampa C, et al. - The seroprevalence of COVID-19 was investigated in a representative population-based cohort in Iquitos, one of the regions with the highest mortality rates from COVID-19 in Peru, where a devastating number of cases occurred in March, 2020. The population-based study of SARS-CoV-2 transmission was carried out at two timepoints: July 13–18, 2020 (baseline), and Aug 13–18, 2020 (1-month follow-up). The 2017 census data were used to derive a geographically stratified representative sample of the city population, which was updated on Jan 20, 2020. People who were inhabitants of Iquitos since COVID-19 was identified in Peru (March 6, 2020) or earlier were included in this work. Overall, 726 eligible individuals were identified and of these, 716 participants (99%) were enrolled, who were distributed across 40 strata (four districts, two genders, and five age groups). The participants were tested for IgG and IgM anti-SARS-CoV-2 antibodies using the COVID-19 IgG/IgM Rapid Test (Zhejiang Orient Gene Biotech, China). A seroprevalence of 70% at baseline and 66% at 1 month of follow-up was identified, with a test-retest positivity of 65%, and an incidence of new exposures of 2%. Per findings, Iquitos had one of the highest rates of seroprevalence of anti-SARS-CoV-2 antibodies worldwide after the first epidemic peak. Nevertheless, a second wave was identified in the city starting in January, 2021, probably due to the emergence of the SARS-CoV-2 P1 variant, which has displayed higher transmissibility and reinfection rates.