Covid-19 causedhospitalizations, severe disease and deaths in any age, including in the youngest children. The aim of this multicenter national study is to characterize the clinical and the prognostic role of lung ultrasound (LUS) in children with Covid-19. We enrolled children between 1 month and 18 years of age diagnosed with SARS-CoV2 infection and whounderwenta lung ultrasound within 6 hours from firstmedical evaluation. A total of 213 children were enrolled, 51.6%were male, median age was2 years and 5 months (IQR 4mm- 11 yearsand4 months).One hundred and fortyeight (69.4%) children were admitted in hospital, 9 (6.1%) in pediatric intensive care unit.We found an inverse correlation between the LUS score and the oxygen saturationatthe clinical evaluation (r = −0.16; p = 0.019). Moreover, LUS scores were significantly higher in patients requiring oxygen supplementation (8 (IQR 3 - 19) vs 2 (IQR 0 - 4); p= 0.001). Among LUS pathological findings, irregular pleural line, sub-pleural consolidations and pleural effusions were significantly more frequentin patients whoneeded oxygen supplementation (p = 0.007; p = 0.006 andp = 0.001, respectively). This multicentric study confirmed that LUS is able to detect Covid-19 low respiratory tract involvement, which is characterized by pleural line irregularities, vertical artifacts and subpleural consolidations. Notably, children with higher LUS score have an higher risk of hospitalization or need for oxygen supplementation, supporting LUS as a valid and safe point-of-care first level tool for the clinical evaluation of children with Covid-19.

Background: The aim of this study was to analyze the lung ultrasound (LUS) patterns in combination with clinical-laboratory profiles of children hospitalized for COVID-19 infection in relation to temporal trend of the Italian epidemic. Methods: This was a retrospective study conducted at a pediatric tertiary referral hospital from 15th March 2020 to 15th March 2021. We compared the characteristics of two periods of the pandemic outbreak, the first one in spring and summer (15th March-30th September 2020) and the second one in autumn and winter (1st October 2020-15th March 2021). Results: 28 patients (53.85%) were in the first period, 24 patients (46.15%) were in the second period. The disease severity score was significantly higher in the second period (p=0.02). We observed that the occurrence of the irregular pleural line was seen more frequently in the second period (87.5% vs 60.71%; p=0.03). The B-lines were significantly more frequent in children in the second period (87.5% vs 60%; p=0.03). The several but not-coalescent B-lines were significantly more frequent in the second period (80% vs 41.7%; p=0.05). The LUS score correlated significantly with the disease severity score with a strong relationship (r=0.51, p=0.002). The second phase of the COVID-19 epidemic outbreak had a higher disease severity score than the first phase with a moderate correlation (r= 0.42; p=0.01). Conclusion: The LUS plays an important role in the evaluation of pulmonary involvement in children affected by COVID-19 during different periods of the pandemic in combination with clinical-laboratory findings.