A Chinese study has found that up to 30% of COVID-19 patients hardly develop any antibodies against the infection, Daily Mail reported.

Fudan University researches found that almost a third of patients have so few antibodies against coronavirus that they are unlikely to have immunity to this infection after recovery, which means that they have a real risk of re-infection.

According to experts, the tests for the search for antibodies, which are now being introduced by many countries, react to the presence of antibodies but do not analyze their level. And if there are too few antibodies, plasma transfusion of patients who have been ill can be useless.

Scientists analyzed the blood plasma of 175 Chinese recovered for the presence of antibodies against coronavirus. It turned out that elderly and middle-aged patients had significantly higher antibody titers in plasma than younger patients. And 10 patients had such low levels of antibodies that they could not be detected using a routine test. About 40% had an average level of antibodies, and only 14% had a high level. On average, patients developed antibodies within 10-15 days after infection.