CD40LG and COVID-19: In a study of longitudinal IgG and IgM response in a large cohort of healthcare workers post-Pfizer-BioNTech COVID-19 mRNA vaccination, 77.4% of naïve vaccinees demonstrated non-canonical immune responses, with 36.1% developing IgG but no IgM response and 41.3% developing IgM after IgG [53].