Anti‐SARS‐CoV‐2 IgG levels in relation to disease severity of COVID‐19

The durability of infection‐induced severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) immunity has crucial implications for reinfection and vaccine effectiveness. However, the relationship between coronavirus disease 2019 (COVID‐19) severity and long‐term anti‐SARS‐CoV‐2 immunoglobulin G (IgG) antibody level is poorly understood. Here, we measured the longevity of SARS‐CoV‐2‐specific IgG antibodies in survivors who had recovered from COVID‐19 1 year previously. In a cohort of 473 survivors with varying disease severity (asymptomatic, mild, moderate, or severe), we observed a positive correlation between virus‐specific IgG antibody titers and COVID‐19 severity. In particular, the highest virus‐specific IgG antibody titers were observed in patients with severe COVID‐19. By contrast, 74.4% of recovered asymptomatic carriers had negative anti‐SARS‐CoV‐2 IgG test results, while many others had very low virus‐specific IgG antibody titers. Our results demonstrate that SARS‐CoV‐2‐specific IgG persistence and titer depend on COVID‐19 severity. Highlights IgG was measured in survivors who had recovered from COVID‐19 1 year previously. Anti‐SARS‐CoV‐2 IgG persistence and titer depend on COVID‐19 severity. The highest virus‐specific IgG titers were observed in survivors with severe COVID‐19. Most asymptomatic carriers were negative for anti‐SARS‐CoV‐2 IgG.