Two new studies show that patients who have recovered from coronavirus rapidly lose antibodies, raising questions over how long immunity to the disease lasts and how reliable antibody testing is.
The studies also highlight the importance the development of a vaccine is to controlling the disease.
One study found that 10 per cent of patients hospitalised with Covid-19 in China had undetectable antibodies just weeks after recovering from the disease.
The study, published on the preprint server medRxiv and not yet peer reviewed, screened 1,500 coronavirus patients in Wuhan for antibodies.
They then compared antibody levels with nearly 20,000 members of the general population, 1,600 patients hospitalised for non-Covid-19 reasons and more than 3,800 health workers who the researchers assumed had been exposed to the virus and therefore had developed antibodies.
They found that one in ten patients who had contracted Covid-19 had no antibodies just weeks after recovering from the disease.
They also found that only five per cent of health workers had antibodies, despite the fact many of them had contracted the disease, and only between one and five per cent of the people in other groups had antibodies.