Originally posted here.
A preprint published last month shows that among 175 recovered COVID-19 patients from Shanghai, 30% showed a low neutralizing antibody response, with 10 patients showing undetectable antibodies.
Fortunately, apart from those 10 cases, serology can generally clearly distinguish between healthy and previously infected individuals.
Antibody levels seem to spike at around 14 days of disease.
There was a robust relationship between age and neutralizing antibody levels, with older patients having higher levels and with the large majority of cases of undetectable antibody levels in the younger patients.
There was no decline in antibody levels when tested two weeks later.
Duration of disease, length of stay, older age, and male gender were each correlated with higher antibody levels.
Those with undetectable antibodies seemed to have a very mild course of disease.
What this study seems to suggest is that serology clearly distinguishes between previously infected individuals and never-infected ones about 95% of the time but not always.
The implications of low antibody producers may yet to be fully understood.