This study, published in the New England Journal of Medicine, investigates the rapid decay of anti-SARS-CoV-2 antibodies in individuals with mild COVID-19. The researchers evaluated 34 participants who had recovered from COVID-19 and referred themselves for observational research. Blood samples were analyzed using enzyme-linked immunosorbent assay (ELISA) to quantify serum anti-receptor-binding domain activity. The results showed that the mean change in IgG levels over the observation period was −0.0083 log10 ng per milliliter per day, corresponding to a half-life of approximately 36 days. The findings suggest that humoral immunity against SARS-CoV-2 may not be long-lasting in individuals with mild illness, raising concerns about the durability of antibody-based immunity and the potential need for caution in implementing strategies such as "immunity passports" and herd immunity. Further studies are needed to define the quantitative protection threshold and the rate of antibody decline beyond 90 days.This study, published in the New England Journal of Medicine, investigates the rapid decay of anti-SARS-CoV-2 antibodies in individuals with mild COVID-19. The researchers evaluated 34 participants who had recovered from COVID-19 and referred themselves for observational research. Blood samples were analyzed using enzyme-linked immunosorbent assay (ELISA) to quantify serum anti-receptor-binding domain activity. The results showed that the mean change in IgG levels over the observation period was −0.0083 log10 ng per milliliter per day, corresponding to a half-life of approximately 36 days. The findings suggest that humoral immunity against SARS-CoV-2 may not be long-lasting in individuals with mild illness, raising concerns about the durability of antibody-based immunity and the potential need for caution in implementing strategies such as "immunity passports" and herd immunity. Further studies are needed to define the quantitative protection threshold and the rate of antibody decline beyond 90 days.