Antibodies to SARS-CoV2 detectable for less than 50 days in polymerase chain reaction confirmed COVID-19 patients

Nishant Kumar, Shibal Bhartiya, Tarundeep Singh


Background: A seroprevalence study for COVID-19 antibodies was conducted amongst health workers in Mumbai, India, in June 2020.

Methods: Healthcare workers (n=801) underwent a cross sectional survey through electrochemiluminescence immunoassay (Roche diagnostics’ Elecsys anti-SARS-CoV-2 assay, Roche diagnostics, Rotkreuz, Switzerland).

Results: Of the 801 healthcare workers, 62 who had been previously diagnosed with a real time-polymerase chain reaction (RT-PCR) proven SARS-CoV-2 infection, 45 (73.6%) were found to be seronegative during the study. The duration between the positive RT-PCR test and the serological testing ranged from 15 to 49 days for 34 (54.8%), and was >50 days in 28 subjects. Up to 28 days after a positive PCR test, 90% of the subjects were found to be seropositive, but this reduced to less than half over the next two weeks (38.5% between 29 and 42 days).

Conclusions: Our findings are in agreement with previous reports that demonstrate a peak antibody formation after 3 weeks, and also an early antibody decay that is almost exponential. This may also have a significant effect on the protection vaccines are able to provide considering that a natural infection has such a transient antibody response.



Real time-polymerase chain reaction confirmed, COVID-19, Seroprevalence, Antibodies

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