RÉSUMÉ
OBJECTIVES: A retrospective study was conducted to identify the prevalence of COVID-19 through serology and RT-PCR in children, adolescents and adults. A database of the COVID-19 Tracking Program in school children was used. METHODS: The data comprised sociodemographic and clinical variables, results of serological tests (IgM and IgG), and real-time-polymerase chain reaction (RT-PCR) results of IgM-positive individuals. The statistical analysis was performed with a 5% significance level. RESULTS: Among 423 children, 107 (25.3%) exhibited seroprevalence with IgG, IgM or IgG/IgM; among 854 adolescents, 250 (29.2%) had positive serology; and among 282 adults, 59 (20.9%) were positive. The frequency of positivity on RT-PCR for SARS-CoV-2 was 3.5%, 3.6% and 6.0% in children, adolescents and adults, respectively. Children had a lower incidence of symptoms than adolescents (p = 0.001) and adults (p = 0.003); the most frequent were fever, ageusia, anosmia, headache, dry cough, sore throat, muscle pain, runny nose, dyspnoea, and diarrhoea. CONCLUSIONS: The prevalence rate for all groups was 26.7% in serology and 4.04% in RT-PCR. Children had lower rates of IgM and fewer symptoms compared with adolescents and adults. The data suggest the potential for transmissibility in all age groups.