TLR4 and COVID-19: The role of S protein binding to TLR4 or TLR2 in the effects of COVID-19 vaccines has never been investigated; however, at least one preprint study exists showing that vaccination of healthy subjects with the BioNTech–Pfizer COVID-19 mRNA vaccine reduced the response of innate immune cells to TLR4 and TLR7/8 ligands, while increasing fungi-induced cytokine responses [45].