The mandatory face mask wearing was implemented in the Czech Republic and Slovakia shortly after the COVID-19 outbreak in Central Europe. So far, the number of COVID-19-associated deaths per 100,000 individuals is far lower in these countries as compared with other neighbouring or close countries. The use of face masks in public may not protect the general public from contracting the virus, however, presumptively decreases the viral load and contributes to a favourable clinical outcome in COVID-19 disease. A certain time is required for antigen-specific T cells and B cells to fully develop. Obligatory face mask wearing in public favours the virus transmission through oral mucosa and/or conjunctival epithelium, which enables the adaptive immune responses to evolve. In the case of inhalation of high loads of SARS-CoV-2, the time for the development of fully protective adaptive immune responses seems to be insufficient. Then, a less specific and more damaging innate immune response prevails.
Keywords: COVID-19; COVID-19 face masks; immunity; transmission route; viral load.