Bronchial alveolar lavage fluid analysis of 3 COVID-19 patients reveals a high number of NKT cells during the acute phase of infection (Kim et al., 2020). This increase in NKT cells was similarly reflected in the peripheral blood. Conversely, a decline in the number of these cells was found during the recovery phase. These results thus suggest a close correlation of the NKT cell activity in COVID-19 and the presence of these cells may be required for the clearance of virus during the initial phase of infection. Concomitantly, increased infiltration and activity of these cells may lead to a more severe outcome associated with eosinophilic pneumonia, as shown in one study. However, no direct correlation of these cells types with disease severity was found, probably due to meagre sample size (n = 3). Further, the samples used in this study were collected at different time points after the onset of symptoms, which may have complicated the interpretation of the results.