KL-6 in mild group was 272.28 ± 95.42 U/mL, compared to 268.04 ± 55.04 U/mL in moderate COVID-19 group (MD = −12.58; 95%CI: −21.59 to −3.57; p = 0.006; Figure 4). The gene discussed is MUC1; the disease is COVID-19.