Interleukin-10 (IL-10) was elevated (median 10.4 pg/ml; percentile range 5.96–30.32; cut-off 5) in 21/22 (95.5%) serum samples (from 12 patients) obtained during hospitalization for COVID-19 in group I. Overall, 11/12 (91.7%) patients showed increased serum levels at least once. Here, IL10 is linked to COVID-19.