Coronavirus antibodies drop by half in less than 90 days and fall faster in younger adults, an ongoing study of staff at the John Radcliffe's hospital trust has revealed.
The paper, published as a pre-print which has not been peer reviewed, presents six months of data from a study of 3,217 Oxford University Hospitals NHS Foundation Trust (OUH) healthcare workers who have attended more than once for antibody testing.
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By measuring antibody responses in the same healthcare workers for up to six months, the researchers could follow what happens to antibody levels over time and how this varied between different people.
In this cohort of working-age healthcare workers, antibody levels rose to a peak at 24 days after the first positive test, before beginning to fall.
Those tested had lost their positive antibody result after an average of 137 days.
John Radcliffe Hospital
The researchers also found that increasing age, Asian ethnicity and prior self-reported symptoms were associated with higher maximum antibody levels.
By contrast, younger adults’ antibody levels fell faster and peaked lower.
One of the authors on the paper, Professor David Eyre of Oxford University’s Nuffield Department of Population Health, said current studies using antibodies to assess how many people have been infected in a population might have missed some.
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He added: "Longitudinal studies like ours are needed to answer some of these important questions about how long and at what level antibodies last, and the extent to which they protect people from reinfection.”
They were among 10,000 staff across OUH’s four hospitals who have been tested both for Covid and antibodies as part of a collaboration between the trust and Oxford University.
Dr Bruno Holthof
When looking at 452 healthcare workers who tested positive, over an average of 121 days, the scientists found the average estimated antibody half-life was between 81 and 90 days.
OUH chief executive Dr Bruno Holthof said: “Since the outbreak of Covid-19, the trust and the university have pooled their resources to develop highly reliable PCR and antibody testing to support the research and care in the fight against the virus.
"I would again like to thank all the people who work at our hospitals who have taken part in this long-term study."
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