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.