Indirect impact on number of admitted children with COVID-19 in the first three months of emergency use of two vaccines, in Rio de Janeiro, Brazil

Introduction: Since January 19, 2021, two vaccines against SARS-COV-2 are available in Brazil for emergency use for selected groups, not including children. Aim: To describe indirect impact on the number of hospitalized children with COVID-19 in the first three months after beginning of emergency use of two vaccines. Methods: A retrospective study was conducted in children (0-18 years), admitted in two pediatric hospitals of Rio de Janeiro city, between January and April 2021 with confirmed COVID-19 by reverse transcription polymerase chain reaction or serological tests. Number of cases, clinical signs, symptoms and outcomes were compared with the first wave of disease (April- June 2020). A p value of less than .05 were considered was significant. Results: The number of total admitted patients (with all diseases) were 1097 in 2020 period, being 46 (4.2%) of them with confirmed COVID-19, and 2187 in the 2021 period, with 47 (2.1%) cases (p=0.006). Predominant respiratory symptoms were present in 29/46 (63%) as the main presentation in 2020 patients and 37/47 (78.7%) in 2021 children (p=0.09). The main symptoms were fever, cough and dyspnoea in both periods. The median of lenght of stay after diagnosis were 4 days in 2020 and 2021 ( p=0.9). Just one patient died in 2021. Conclusion: There was reduction of relative percentage of admitted confirmed pediatric cases in the the first three months of emergency use of two vaccines against SARS-COV-2, but it is uncertain to atribute this finding to vaccination due to high circulation of the virus in the city.