Protective mucosal SARS-CoV-2 antibodies in the majority of the general population in the Netherlands.

Antibodies to SARS-CoV-2 on the mucosal surfaces of the respiratory tract are understood to contribute to protection against SARS-CoV-2 infection. We aimed to describe the prevalence, levels, and functionality of mucosal antibodies in the general Dutch population. Nasal samples were collected from 778 randomly selected participants, 1-90 years of age, nested within the nationwide prospective SARS-CoV-2 PIENTER corona serosurvey in the Netherlands. Spike-specific immunoglobulin (Ig)G was detected in the nasal samples of 94.6% (in case of the wild-type S1 variant) and 94.9% (Omicron BA.1) of the individuals, whereas 44.2% and 62.7% of the individuals were positive for wild-type and Omicron BA.1 S1 IgA, respectively. The lowest prevalence of mucosal antibodies was observed in children under 12 years of age. The prevalence and levels of IgA and IgG were higher in individuals with a history of SARS-CoV-2 infection. Mucosal antibodies inhibited the binding of Wuhan, Delta, and Omicron BA.1 receptor binding domain to human angiotensin-converting enzyme 2 in 94.4%, 95.4%, and 92.6% of the participants, respectively. Higher levels of mucosal antibodies were associated with a lower risk of future infection.