Wan S, Yi Q, Fan S, et al. - Researchers investigated if and how lymphocyte subsets, cytokines, pulmonary inflammation index (PII) are associated with disease evolution in patients with (corona virus disease 2019) COVID‐19. Among a total of 123 included patients with COVID‐19, there were 102 mild and 21 severe patients. The two groups exhibited significant differences in cluster of differentiation 4 (CD4⁺ T), cluster of differentiation 8 (CD8⁺ T), interleukin 6 (IL‐6), interleukin 10 (IL‐10) and PII. The mild group had significant positive correlations between CD4⁺ T and CD8⁺ T, IL‐6 and IL‐10. After ‘five‐in‐one’ treatment, all patients were discharged with the exception of the four who died. The mild group and those with IL‐6 within normal values had higher survival rates. Findings suggest a possible utility of CD4⁺ T, CD8⁺ T, IL‐6, IL‐10 and PII as indicators of disease evolution, and of PII as an independent indicator for disease progression of COVID‐19.