As visualised in Figure 2, a majority of patients with a high percentage of activated CD4+ T-lymphocytes and low percentages of CTLA-4+ T-lymphocytes and immature B-lymphocytes had pneumonia, a history of hospitalisation, impaired lung function, and persistent dyspnoea at the post-COVID-19 check-up. Here, CTLA4 is linked to susceptibility to pneumonia measurement.