This is an observational longitudinal study to assess incidence of SARS-CoV-2 infection in Brazil. The study sample is stratified in nine age groups according decades of life, equally distributed in both sexes, with an expected incidence of 10%, at least, during the study period of 24 months. For the first age groups, (0-9, 10-19 and 20-29 years), sample was calculated with the minimum expected incidence of COVID-19 among infected, regardless severity, is 10%. For the latest age groups (30-39, 40-49, 50-59, 60-69, 70-79 and 80+), the sample was calculated with the expected minimum incidence of hospitalization due to COVID-19 according to estimates per age group reported by Verity R et al. https://doi.org/10.1016/S1473-3099(20)30243-7 After the consent procedure, all participants will have a short interview, a IgG/IgM SARS-CoV-2 rapid test and a blood withdrawal to obtain serum for neutralizing antibodies. These procedures will be repeated every four weeks until the end of the study. Individuals with symptoms compatible will be followed-up to confirm COVID-19 diagnosis as well as to assess severity, need for hospitalization and assisted ventilation, sequels, and eventual reinfection. Levels of neutralizing antibodies and other immune markers will be prospectively assessed in all infected participants, either asymptomatic and symptomatic.
