Impact of Variants, Epidemiological Trends, and Comorbidities on Hospitalization Rates of Unvaccinated Children in Brazil: A Retrospective Study (2020-2022).

This retrospective study aimed to investigate the impact of the emergence of new variants and the epidemiological scenario on hospitalization rates of unvaccinated children (0-12 years) in Brazil. The study included 1614 children admitted to a hospital between March 2020 and December 2022 but 101 (6.3%) of them testing positive for COVID-19 via RT-PCR. The frequency of COVID-19 cases increased from 7.5% in 2020 to 9.3% in 2022 with the emergence of the Omicron variant. Children over 5 years old with comorbidities accounted for most cases (69% [70/101]). Sickle cell anemia was the most frequent comorbidity (20%), and influenza-like illness (36% [36/101]) and decompensation of underlying disease (33% [33/101]) were the main reasons for hospitalization. Coinfection was detected in 11% of cases, with respiratory syncytial virus (RSV) being the most common viral pathogen (71%). Hospital readmission occurred in 26% of cases, with a higher frequency in children over 5 years old. The death rate was 1.9%, with comorbidities such as cystic fibrosis and congenital heart disease as risk factors. These findings emphasize the need to prioritize vaccination with monovalent Omicron XBB for high-risk groups, including children over 5 years old with comorbidities, to mitigate the impact of new variants and reduce severe disease outcomes.