BACKGROUND: The COVID-19 pandemic reached the Southern Hemisphere in the autumn of 2020, thus coinciding with its expected annual viral respiratory season. The potential impact of national strategies aimed at mitigating COVID-19 during the pandemic on the incidence of other critical viral lower respiratory tract infections (LRTIs) in children is unknown. METHODS: We analysed admission data for LRTIs from 22 paediatric intensive care units (PICUs) in four countries, part of a large international Latin American registry of children with acute respiratory failure (Red Colaborativa Pediátrica de Latinoamérica [LARed Network]). RESULTS: Between January and August, there were 83% fewer PICU admissions for LRTIs in 2020 compared to the 2018/2019 average over the same period. Similar decreases were noted for PICU admissions due to respiratory syncytial virus and influenza (92% and 78%, respectively). CONCLUSION: We observed a striking reduction in PICU admissions due to viral LRTIs over winter, during the COVID-19 pandemic in South America.