Supplementary Material for: Exhaled Breath Condensate and Respiratory Sequelae in Children Post-COVID-19

<b><i>Background:</i></b> Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes an acute respiratory illness. A substantial proportion of adults experience persistent symptoms. There is a paucity of data on respiratory sequelae in children. Exhaled breath condensate (EBC) is a non-invasive tool used to assess airway inflammation. <b><i>Objectives:</i></b> This study aimed to evaluate EBC parameters, respiratory, mental and physical ability among children post COVID-19 infection. <b><i>Methods:</i></b> Observational study of confirmed SARS-CoV-2 infection cases among children, aged 5–18 years, evaluated once, 1–6 months post positive SARS-CoV-2 PCR testing. All subjects performed spirometry, 6-min walk test (6MWT), EBC (pH, interleukin-6), and completed medical history questionnaires, Depression, Anxiety, and Stress Scale (DASS-21), and physical activity scores. Severity of COVID-19 disease was classified according to WHO criteria. <b><i>Results:</i></b> Fifty-eight children were included and classified asymptomatic (<i>n</i> = 14), mild (<i>n</i> = 37), and moderate (<i>n</i> = 7) disease. The asymptomatic group included younger patients compared to the mild and moderate groups (8.9 ± 2.5y vs. 12.3 ± 3.6y and 14.6 ± 2.5y, respectively, <i>p</i> = 0.001), as well as lower DASS-21 total scores (3.4 ± 4 vs. 8.7 ± 9.4 and 8.7 ± 0.6 respectively, <i>p</i> = 0.056), with higher scores in proximity to positive PCR (<i>p</i> = 0.011). No differences were found between the 3 groups regarding EBC, 6MWT, spirometry, body mass index percentile, and activity scores. <b><i>Conclusions:</i></b> COVID-19 is an asymptomatic-mild disease in most young healthy children, with gradually diminishing emotional symptoms. Children without prolonged respiratory symptoms revealed no significant pulmonary sequelae as evaluated by EBC markers, spirometry, 6MWT, and activity scores. Larger studies are required to assess long-term pediatric consequences of post SARS‐CoV‐2 infection, to assess the need for pulmonology surveillance.