Results
The incidence of positive RT-PCR was lower in residents vaccinated by two doses (22.7%) vs one dose (32.3%) or non-vaccinated residents (43.7%)(p<0.01). Covid-19-induced deaths were observed in 10.4% of the non-vaccinated residents, in 6.4% of those who had received one dose, and in 0.9% with two doses (p=0.0007). Severe symptoms were more common in infected non-vaccinated (21.0%) vs vaccinated residents (47.6%, p=0.002). Higher levels of RBD-IgG (n=325) were associated with a lower SARS-CoV-2 incidence. No in vitro serum neutralization activity was found for RBD-IgG levels below 1,050 AU/mL. RBD-IgG levels were inversely associated with N-Ag levels, found as a risk factor of severe Covid-19.