Seroprevalence of anti-SARS-CoV-2 antibodies in Iquitos, Loreto, Peru

Background Detection of SARS-CoV-2 antibodies among people at risk is critical for understanding both the prior transmission of COVID-19 and vulnerability of the population to the continuing transmission and, when done serially, the intensity of ongoing transmission over an interval in a community. In this study, we estimated the seroprevalence of COVID-19 in a representative population-based cohort of 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. Methods We conducted a population-based study of transmission tested each participant using the COVID-19 IgG/IgM Rapid Test from Orient Gene Biotech and used survey analysis methods to estimate seroprevalence accounting for the sampling design effect and test performance characteristics. Here we report results from the baseline (13 to 18 July 2020) and the first month of follow-up (13 to 18 August 2020) study. Findings We enrolled a total of 716 participants and estimated seroprevalence of 70.0% (95% CI: 67.0%–73.4%), a test-re-test positivity of 65% (95% CI: 61.0%–68.3%), and an incidence of new exposures of 1.8% (95% CI: 0.9%–3.2%) data that suggest that transmission is ongoing but is occurring at low levels. We observed significant differences in the seroprevalence between age groups, with participants 18 to 29 years of age having lower seroprevalence than children <12 years of age (Prevalence ratio =0.85 [PR]; 95% CI: 0.73 – 0.98), suggesting that children were not refractory to infection in this setting. Interpretation Iquitos demonstrates one of the highest rates of seroprevalence of COVID-19 worldwide. Current data shows a limited case burden in Iquitos for the past seven months and suggests that these levels are sufficient to provide significant but incomplete herd immunity. Funding Dirección Regional de Salud de Loreto, DIRESA, Loreto, Peru ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was completely finance by Direccion Regional de Salud de Loreto, DIRESA, Loreto, Peru ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the hospital health network Institutional Scientific Committee and Institutional Review Board of the Regional Hospital, Iquitos, from Peru. All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The authors confirm that the data supporting the findings of this study are available within the article.