Immunity to Covid-19 rapidly declines, research shows

Two new studies show that patients that have recovered from coronavirus rapidly lose antibodies, raising questions over the length of time immunity to the illness lasts and how reliable antibody testing is.
The studies also highlight the importance the development of a vaccine is to controlling the illness.
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The study, published on the preprint server medRxiv and not yet peer reviewed, screened 1,500 coronavirus patients in Wuhan for antibodies.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 not quite 20,000 members of the general populace, 1,600 patients hospitalised for non-Covid-19 reasons and much more than 3,800 health workers who the researchers assumed was exposed to the virus and for that reason had developed antibodies.
They found that one in ten patients who had contracted Covid-19 had no antibodies just weeks after coping with the disease.
They also unearthed that only five per cent of health workers had antibodies, despite the fact most of them had contracted the disease, and only between one and five % of individuals in other groups had antibodies.
The fact that one in 10 patients lost antibodies so fast and thus few health workers developed antibodies showed that “after SARS-CoV-2 infection, people are unlikely to produce long-lasting protective antibodies against this virus”, the researchers concluded.
The other antibody study, published in the journal Nature Medicine, compared two categories of people who contracted the disease in Wanzhou, China in February. They looked over 37 those who had asymptomatic cases of the disease and 37 who had more serious forms.
They found that 40 per cent of individuals in the asymptomatic group had undetectable levels of antibodies two to three months following the infection, compared to 13 per cent in the group who had a more severe dose of the disease.
Prof Liam Smeeth, professor of clinical epidemiology at the London School of Hygiene and Tropical Medicine, commenting on the Nature Medicine study, said there were “marked reduction” in immunity among those who had apparent symptoms of Covid-19.
“This strongly suggests that immunity may well diminish within months of infection for a substantial proportion of people. We need larger studies with longer follow-up in more populations, but these findings do suggest that we cannot rely on people having had proven infections nor on antibody testing as strong evidence of long term immunity.”
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