Publication date: Feb 01, 2025
Worldwide, respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections (LRTIs) and hospital admissions among infants and young children. The COVID-19 pandemic changed the epidemiology and clinical patterns of respiratory viruses other than severe acute respiratory syndrome coronavirus 2. Argentina introduced the RSV maternal vaccine in 2024. This multicenter study describes the clinical-epidemiological profile of hospitalized pediatric patients with LRTI associated with RSV in Argentina, comparing pre- and postpandemic periods, and identifies independent predictors of RSV infection. This prospective, multicenter study included patients under 18 years old admitted for LRTI in 5 tertiary centers in Argentina before (2018-2019) and after (2022-2023) COVID-19. Changes in viral detection rates, seasonality, epidemiological and clinical characteristics were analyzed. Indirect immunoassay or real-time polymerase chain reaction were used for virological diagnosis prepandemic and real-time polymerase chain reaction for postpandemic. Data analysis was performed using Epi Info 7. A total of 5838 LRTI cases were included (mean age: 9. 5 months; interquartile range: 4-22 months), with 96. 6% tested for viral detection, and 66. 4% positive (3877 cases). RSV was the most prevalent virus, followed by parainfluenza and influenza. Postpandemic, there was a significant decrease in RSV prevalence and an increase in parainfluenza and metapneumovirus infections. LRTI seasonality shifted 6 weeks forward postpandemic. In 2022, metapneumovirus cases increased, displacing RSV, which recovered prevalence and typical seasonality in 2023 with an earlier onset. Viral coinfection occurred in 17. 2% of RSV cases. Globally, 71% of RSV cases were infants under 12 months (45. 8%,