This is an observational study, meaning that no interventions is tested, to determine incidence of SARS-CoV-2 infection and COVID-19 in different clinical sites in Brazil in several age groups. The study aims to assess baseline number of infected participants and perform a follow-up along two years to determine the new cases occurring among participants during the period. All participants will collect blood samples to get more details on the immune response.

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.

Inclusion Criteria:

• Any sex or age
• Providing informed consent
• Agreement with all study visits, procedure and contacts

Exclusion Criteria:

• Previous suspected or confirmed COVID-19
• Febrile illness in the latest 72 hours
• Olfactory or gustatory dysfunction in the last three months
• Healthcare worker in a service with routine attention to COVID-19 patients
• Any conditions that can might hurdle participant's compliance to the study in tha opinion of the study team

The sample size will be equally distributed in ten different cities of Brazil. Then, each site will have same representation of each age group. Participants can be selected from other ongoing community-based studies conducted in the site and from community in general. Balance of participant according to sex is recommended to the sites in all age group.