CD19 and influenza: The active COVID-19 cohort showed substantial expansions of CD20dim/− PBs averaging 19.15% (range 1.87%–60.4%) of circulating CD19+ B cells, whereas increased levels of CD20dim/− PBs were not observed 14 (+/−7) days after influenza vaccination (mean 4.19%, range 1.12%–9.81%) or in healthy individuals (3.3%, range 1.73%–6.05%) (Figures 1A and 1C).