Length of hospitalization is associated with sustained IgG titer against SARS-CoV-2 spike protein.

130 patients out of 147 (patients with less than 7 days of hospitalization were excluded) were categorized into three separate categories (th, 25th-75th and >75th percentiles of all EC50 values) according to their corresponding sustained IgG response, which was maintained for at least 5 consecutive days during hospitalization. Out of the 130 patients, 21 patients with IgG titer fluctuating between the three established categories were separated into an intermediate category. Kruskal-Wallis test shows a significant association between the LOS and sustained IgG categories (p value = 1.2x10-3).