PROS1 and COVID-19: On the other hand, administration of the viral S protein (by the BNT162b2 mRNA vaccine) triggers a significant mobilization of adaptive immune responses already at D22 which, following the second dose, plateaus at values (97.231% median inhibition) higher not only from pooled COVID-19 patients (Fig. 4; D39 versus D36), but even from COVID-19 patients with severe disease (group 2) (90.02% median inhibition) (P < 0.0001).