TNF and COVID-19: The expression levels of activation-induced cell death (AICD)-related genes possibly mediated by TNF pathway (20, 21) were significantly elevated by vaccination in all T cell subtypes of both COVID-19 naive individuals and COVID-19 convalescents, but their expression levels in convalescents were much higher than those in COVID-19 naive individuals (P = 4.1 × 10−3) (Fig. 5B).