CD19 and infection: Furthermore, the percentage of CD19+ cells in blood samples from patients with moderate COVID-19 was significantly lower than that in the healthy donors (8.7 (6.2;12.2)% vs. 11.4 (9.5;15.3)%, p = 0.020), whereas in patients with severe infection it was almost the same (11.1 (7.5;18.2)%).