Background and Objective:
In September 2022, there were 34.7 million cases of COVID-19 in Brazil, corresponding to 6% of the world total and resulting in a calamity that affected the health and living conditions of millions of Brazilians. The course of the disease in children appears to be milder than in adults. However, severe forms can also occur, often requiring hospitalization and support in intensive care units (ICU). The objective of the study was to analyze morbidity due to COVID-19 and hospitalization due to Severe Acute Respiratory Syndrome (SARS) among children living in Rio de Janeiro state, between March 2020 and December 2021.

Methods:
Population-based ecological study, using secondary data from the Center for Strategic Information and Response in Health Surveillance (CIEVS-RJ). Incidence rates were calculated according to age group (0-4, 5-9 and 10-19 years) and epidemiological week (Epi Week). Trends were analyzed using the Joinpoint Regression Analysis program.

Results:
117,736 cases of COVID-19 were reported; 64.1% of which among 10-19 year olds. Highest incidences occurred after the emergence of the Delta variant in the country, in June 2021. A 385% increase in the proportion of cases among children less than 19 years of age was observed between March 2020 and November 2021. There were 3,476 hospitalizations due to SARS; 39% required utilization of ICU. A 6.8% case-fatality rate was observed, reaching 10.4% among those 10-19 years. After the introduction of COVID-19 immunization in children 12 years and older, there was a significant 15.6% reduction in hospitalizations per Epi Week among children 10-19 years. Decreases in other age groups were less pronounced.

Conclusion:
Our results should inform the planning for strategies and actions by public health managers as well as encourage recommendations towards the effective implementation of the immunization program among children and adolescentes in Brazil.