PDCD1 and Recurrent upper respiratory tract infections: The incidence rates for adverse events of applied PD-1 inhibitor therapy were as follows: the incidence rate of grades 1–5 cough was 0.171 (95%CI: 0.077–0.376, I2 = 95.68%); the incidence rate of grades 1–5 pneumonitis was 0.112 (95%CI: 0.042–0.296, I2 = 93.28%); the incidence rate of grades 1–5 upper respiratory tract infection was 0.061 (95%CI: 0.039–0.084, I2 = 0%); the incidence rate of grades 3–5 pneumonitis was 0.049 (95%CI: 0.021–0.088, I2 = 86.96%).