In a new study, researchers found that COVID-19 antibodies remain stable in the blood of the majority of infected individuals almost two months after diagnosis and possibly longer.
However, antibodies were not detectable in everyone exposed to the virus, opening discussions on how best to interpret antibody and viral tests.
The findings give answers to questions around how long people may remain immune after exposure to COVID-19 and provide insight into how different age and ethnic groups respond to infection.
The research was led by a team and clinicians at St George’s and elsewhere.
The study is an analysis of antibody test results from 177 individuals diagnosed with COVID-19 infection from a viral test.
The team measured the levels of COVID-19 antibodies in patients exposed to the virus.
The results demonstrate that in those patients with an antibody response, the levels remained stable for the duration of the study (almost two months).
The study also shows that those patients with the most severe infections having the largest inflammatory response were more likely to develop antibodies.
The researchers suggest that this may be due to antibody responses working in parallel with an inflammatory response to severe disease, or that a higher viral load could lead to greater stimulation of the inflammatory and antibody development pathways.
Further mechanistic work is required to understand if and why this may be the case.
Between 2 and 8.5% of patients did not develop COVID-19 antibodies at all.
The researchers indicate this may be because the immune response in these patients could be through other immune response mechanisms, such as different antigens or T-cells.
Another option could be that relatively mild infection may be restricted to particular locations in the body, such as within mucosal cells of the respiratory tract, where antibody responses are instead dominated by a secretory immune system.
The study also explored associations between different characteristics and antibody responses.
Being of non-white ethnicity was associated with a higher antibody response, tying into the knowledge that patients from BAME backgrounds are more likely to develop severe disease.
Older patients and those with other conditions, such as hypertension and being overweight were also more likely to have an antibody response.
One author of the study is Professor Sanjeev Krishna from St George’s, University of London.
The study is published on the pre-print server medRxiv.
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