Authors reply: Evaluation of SARS-CoV-2 antibody levels on hospital admission as a correlate of protection against mortality

BackgroundMillions of people have now been vaccinated against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, it is still unclear which antibody levels provide protection against mortality. It is further unknown whether measuring antibody concentrations on hospital admission allows for identifying patients with a high risk of mortality. ObjectivesTo evaluate whether anti-SARS-CoV2-spike antibodies on hospital admission predict in-hospital mortality in patients with coronavirus disease 2019. MethodsWe conducted a prospective, multicentre cohort study on 1152 hospitalized patients who tested positive for SARS-CoV-2 with a polymerase chain reaction-based assay. Patients were classified by vaccination status. Anti-SARS-CoV-2 spike antibodies were determined on hospital admission. The investigated end point was in-hospital mortality for any cause. ResultsSpike antibodies on hospital admission were significantly lower in non-survivors in both non-vaccinated (73 U/ml, 95%CI 0-164 vs. 175 U/ml, 95%CI 124-235, p = 0.002) and vaccinated patients (1056 U/ml, 95%CI 701-1411 vs. 1668 U/ml, 95%CI 1580-1757, p < 0.001). Further, spike antibodies were significantly lower in fully vaccinated and boostered patients who died compared to those who survived (mean 883 U/ml, 95%CI 406-1359 vs. 1292 U/ml, 95%CI 1152-1431, p = 0.017 and 1485 U/ml, 95%CI 836-2133 vs. 2050 U/ml, 95%CI 1952-2149, p = 0.036). Patients infected with the currently prevailing Omicron variant were three times more likely to die if spike antibodies were <1200 U/ml (OR 3.458, 95%CI 1.562-7.656, p = 0.001). After adjusting for potential confounders, this value increased to an aOR of 4.079 (95%CI 1.809-9.198, p < 0.001). ConclusionAnti-SARS-CoV2 spike-antibody levels on hospital admission are inversely associated with in-hospital mortality. Hospitalized patients with lower antibody levels have a higher risk of mortality.