It is now well established that most COVID-19-recovered individuals develop IgM, IgG, and IgA antibodies within the first two weeks after symptom onset (93–102), and that SARS-CoV-2 vaccination induces IgM and IgA responses, albeit not in all individuals and of a more transient nature than IgG responses (103–112). Here, CD40LG is linked to COVID-19.