Evaluation of SARS‐CoV‐2 antibody levels on hospital admission as a correlate of protection against mortality

Background Millions 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. Objectives To evaluate whether anti‐SARS‐CoV2‐spike antibodies on hospital admission predict in‐hospital mortality in patients with coronavirus disease 2019. Methods We 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. Results Spike 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