Moreover, both higher frequencies of transitional CD19+CD38+IgMhigh B cells (AUC 65.4%; 95% CI 57.4% to 73.5%; P < .001) as well as CD19+CD38+IgM‐ plasmablasts (AUC 70.3%; 95% CI 62.3 to 78.2%; P < .001) significantly discriminated COVID‐19 convalescent individuals from HC. Here, CD40LG is linked to COVID-19.