“In four of our nine patients, we found a drop in neutralising antibodies in a special test that can only be carried out in a high-security laboratory,” Wendtner said. “The impact on long-term immunity and vaccination strategies remains speculative but this needs to be monitored,” he continued.
The results suggest that recovered patients could become re-infected with coronavirus, although further tests have yet to confirm this.
The body’s immune response consists of B cells, which secrete antibodies, and T cells, which are capable of recognising and killing previously detected antigens. Both are necessary for long-term immunity.
Wendtner’s findings are consistent with other studies around the world. Chinese researchers reported in the journal Nature that the presence of coronavirus antibodies in the blood decreased sharply after two months. This was especially true for asymptomatic patients, who produced fewer antibodies and a lower immune response.
Other studies, including in Belgium and Spain, have also seen low levels of antibodies among their populations.
In contrast, in Sweden, researchers at the Karolinska Institute and the Karolinska University Hospital suggested that “roughly twice as many people have developed T-cell immunity compared with those who we can detect antibodies in.” T-cells are “a type of white blood cells that are specialised in recognising virus-infected cells.”
For the moment, infections continue to rise, with 12,322,395 confirmed cases of coronavirus and 556,335 people who have passed away from it, according to the World Health Organisation (WHO).