Posted on 21 June 2020
A new study published in Nature Medicine showed that antibodies to SARS-CoV-2 faded quickly in both asymptomatic, and symptomatic COVID-19 patients. This could have major implications on nationwide lockdowns, and antibody testing.
The study focused on 37 asymptomatic, and 37 symptomatic patients in the Wanzhou District in China. Regardless of whether the patients were asymptomatic or not more than 90% of both groups showed steep declines in levels of SARS-COV-2–specific immunoglobulin G (IgG) antibodies within 2 to 3 months after onset of infection. Further, 40% of the asymptomatic group tested negative for IgG antibodies 8 weeks after they were released from isolation.
The results presented in this study could have significant societal implications. The authors of this study said the findings suggest that it could be risky to assume that recovered patients are immune to reinfection, which may have implications for how long to maintain physical distancing restrictions. In addition, this study also highlights that the plasma from COVID-19 survivors may not be suitable for treating other patients after these three months have passed. Governments may also need to revise the concept of herd immunity, and recognize that people who have already had COVID-19 may fail antibody tests after three months.
However, the lack of antibodies in patients who have previously had COVID-19 is not an indication that the same person can be infected with COVID-19 a second time after only three months. The human immune system also has a backup system that stores memories of previous pathogens. When encountered by a known attacker like SARS-CoV-2 the immune system could mass produce the neutralizing antibodies that can block it. Serendipitously a new research paper publish in Nature observed that even a small amount of antibody would be sufficient to achieve a correct response to SARS-CoV-2.
Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections: https://www.nature.com/articles/s41591-020-0965-6
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): https://en.wikipedia.org/wiki/Severe_acute_respiratory_syndrome_coronavirus_2
Convergent antibody responses to SARS-CoV-2 in convalescent individuals: https://www.nature.com/articles/s41586-020-2456-9