Our results also demonstrated that COVID-19 patients, particularly those with PASC, display (i) higher levels of IFN-β and IFN-λ (this latter being associated with mucosal microbial defences) and (ii) specific anti-S IgA, which are short-lived Ig compared to IgG, and mostly induced in mucosal tissues. Here, IFNB1 is linked to long COVID-19.