A study published in the New England Journal of Medicine found that anti-SARS-CoV-2 antibodies in individuals with mild Covid-19 decline rapidly. The research, conducted by a team at the David Geffen School of Medicine at UCLA, analyzed blood samples from 34 individuals who had recovered from mild Covid-19. Blood samples were collected at intervals of up to 86 days after symptom onset. The study found that the average half-life of anti-SARS-CoV-2 receptor-binding domain (RBD) IgG antibodies was approximately 36 days, with a mean decline rate of -0.0083 log10 ng per milliliter per day. This rapid decay suggests that immunity from mild infection may not be long-lasting. The study also noted that antibody levels were more consistent with those reported by Long et al. than with those for SARS-CoV-1. The researchers caution that the findings raise concerns about the durability of humoral immunity against SARS-CoV-2, particularly in light of the short-lived immunity against common human coronaviruses. The study highlights the need for further research to determine the quantitative protection threshold and rate of decline of antiviral antibodies beyond 90 days. The study was supported by several grants and foundations. The authors disclose no conflicts of interest. The study was published on July 21, 2020, and last updated on July 24, 2020.A study published in the New England Journal of Medicine found that anti-SARS-CoV-2 antibodies in individuals with mild Covid-19 decline rapidly. The research, conducted by a team at the David Geffen School of Medicine at UCLA, analyzed blood samples from 34 individuals who had recovered from mild Covid-19. Blood samples were collected at intervals of up to 86 days after symptom onset. The study found that the average half-life of anti-SARS-CoV-2 receptor-binding domain (RBD) IgG antibodies was approximately 36 days, with a mean decline rate of -0.0083 log10 ng per milliliter per day. This rapid decay suggests that immunity from mild infection may not be long-lasting. The study also noted that antibody levels were more consistent with those reported by Long et al. than with those for SARS-CoV-1. The researchers caution that the findings raise concerns about the durability of humoral immunity against SARS-CoV-2, particularly in light of the short-lived immunity against common human coronaviruses. The study highlights the need for further research to determine the quantitative protection threshold and rate of decline of antiviral antibodies beyond 90 days. The study was supported by several grants and foundations. The authors disclose no conflicts of interest. The study was published on July 21, 2020, and last updated on July 24, 2020.