Association of baseline antibody profile with clinical outcomes and viral load
hospitalization/death, IgA and IgG antibodies were 7.17 (SD
VIRUS
The presence of IgA and/or IgG antibodies at baseline was associated with differences in clinical outcomes. For seronegative patients who received placebo, 4.5% (39/860; 95% CI 3.2‒6.2) were hospitalized or died. For patients who received placebo and were IgA-positive only (i.e., positive on anti-S1 IgA, negative on both anti-S1 IgG and anti-N IgG) at baseline, the proportion of hospitalization/death was 3.9% (7/181; 95% CI 1.6‒7.8). However, for patients who received placebo and were both IgA- and IgG-positive (i.e., positive on anti-S1 IgA and positive on anti-S1 IgG or anti-N IgG), the proportion was 0.7% (1/167; 95% CI 0.01‒3.3), an 86.7% risk reduction compared with seronegative patients.The association between antibody class and viral load was also examined at baseline. The viral loads (log10 copies/mL) for seronegative patients, those with IgA but not IgG, and those who had developed both IgA and IgG antibodies were 7.17 (SD: 1.46), 5.77 (SD: 1.59), and 4.36 (SD: 1.42), respectively, demonstrating a strong additive effect of IgG and IgA (40-fold decrease) relative to IgA alone on clearing the virus. Among the seropositive patients, the viral loads (log