Notably, these two groups of pneumonia patients showed no significant differences, except for the number of naïve CD8+ cells, which were markedly lower in Pn+PCR+ patients than in the Pn+PCR− group in both absolute (0.047 [0.026–0.110] × 103/μL vs. 0.155 [0.063–0.277] × 103/μL; p < 0.01, respectively) and percentage (relative) terms (19.39 [9.55–29.98]% vs. 31.97 [19.25–49.63]% of total lymphocytes; p < 0.05). Here, CD8A is linked to susceptibility to pneumonia measurement.