Publications

Previous studies have shown that neutralizing and binding antibody titers are correlates of protection for symptomatic SARS-CoV-2 infection. We previously reported that individuals with low IgG and IgA baseline immune history (BIH) to SARS-CoV-2 variants were at increased risk of symptomatic infection in study of healthcare workers that received 3 or 4 doses of the Pfizer BNT-1262b2 vaccine. We also found that 1-month post-vaccination with the 4th booster dose, individuals with low-BIH mounted significant rises in binding and neutralizing antibody titers, to levels comparable to those of individuals with high-BIH, demonstrating that their increased risk was not due to inability to respond to vaccination. To further study the underlying factors that are associated with increased risk, we conducted a systems serology study of 40 low-BIH and 40 high-BIH individuals across 7 months of follow-up. We found that individuals with low BIH exhibited a significantly higher risk of symptomatic infection (HR=2.691, p=0.0065) and mounted weaker IgA and antibody-dependent cellular cytotoxicity (ADCC) responses compared to high-BIH individuals, particularly against Omicron and Delta variants. Baseline levels of the chemokine CXCL-11 were elevated in the low-BIH group. We then showed that baseline immune profiles can be used to train a prediction model of infection risk across 7 months of follow-up with 76% accuracy. IgA, ADCC and ADCP baseline features were dominant predictors of susceptibility. Our findings suggest that non-neutralizing antibody functions, especially IgA and ADCC, contribute to protection against symptomatic SARS-CoV-2 infection and that serology-guided stratification can enhance discovery of immune correlates of risk informing future vaccine design and deployment strategies.