How Long Does It Take for COVID-19 Patients to Develop Antibodies?
BACKGROUND AND PURPOSE:
Data regarding time course to develop antibody response to SARS-CoV-2 is limited
Zhao et al. (Clinical Infectious Diseases, 2020) investigated the dynamics of total antibody (Ab), IgM and IgG antibodies against SARS-CoV-2 in a series of blood samples taken from patients with confirmed COVID-19
Shenzhen Third People’s Hospital, China
Acute respiratory infection syndromes and/or abnormalities in chest CT images accompanied by detectable SARS-CoV-2 RNA in respiratory sample since illness onset (COVID-19 Diagnosis Based on National Health Commission of China Protocol)
All in critical condition requiring ventilation (invasive or non-invasive)
Enzyme linked immunosorbent assays (ELISA) were performed on successive plasma samples to determine
Total antibodies (Ab) against SARS-CoV-2 (specificity 99.1%)
IgM antibody (specificity: 98.6%)
IgG antibody (specificity: 99.0%)
Antibody dynamics analyzed during disease progression
173 patients | 535 plasma samples
Negative antibody findings: 12 patients
These patients had samples taken earlier in their disease course (10 <day 10; 2 on day 11 and 13 after onset)
Median seroconversion time
Ab: day 11
IgM: day 12
IgG: day 14
<40% of patients had antibodies within 1 week of disease onset
>15 days after onset, antibody testing was more sensitive, detecting a greater percentage of patients with COVID-19
Combining RNA and antibody detection significantly improved sensitivity (p<0.001)
This was true even in the early stages of disease (<1 week since onset; p=0.007)
A higher titer of Ab was independently associated with a worse clinical classification (p=0.006)
Antibodies against SARS-CoV-2 were present in 100% of COVID-19 patients after 15 days since disease onset
Antibodies were only detected in 40% of patients within 1 week of disease onset
The authors highlight important points related to antibodies, including
This study could not evaluate the persistence of antibodies because samples were collected during the acute phase
Cross-reactivity of the assay to other coronaviruses needs to be further assessed
The authors suggest that combining serological antibody tests with the PCR-based tests for viral RNA could improve the accuracy of disease diagnosis
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