* The second RT-PCR was performed 7 days after the first positive RT-PCR
result in 47 residents; **Analysis using Kruskal-Wallis test; ***
Analysis using Fisher test; ****Analysis using ANOVA; *****Analysis
using Mann-Whitney test; ****** level of detection of the assay is 2.95
ng/mL. Samples with Nucleocapside Ag level over 180 pg/mL were diluted.
Titer is the number of dilution possible, still reaching the detection
threshold. According to the manufacturer of the SARS-CoV-2 IgG II Quant
assay (Abbott Diagnostics), the positive threshold is of 50 AU/mL
RBD-IgG levels. Based on previous studies, an RBD-IgG level ≥ 1,050
AU/mL is considered as a significant antibody response to the vaccine,26 and a level ≥ 4,160 AU/mL indicates a high
neutralizing effect against SARS-CoV-2 27.