TCell immunity persists . . . .19 Nov 2020 03:17
In yesterday's DT :-
"Researchers find immunity remains for minimum of eight months, fuelling hope vaccines could protect population for years (By Laura Donnelly, Health Editor 18 November 2020)
Immunity to coronavirus lasts at least eight months and may even last for years, new research suggests. A study of 185 Covid survivors looked at multiple types of immune cells, including those that store the "memory" of the virus, that can activate antibodies when they encounter a new threat. The study, led by scientists at the La Jolla Institute for Immunology, part of the University of San Diego, is one of the largest so far, assessing several elements of the immune response including antibodies and T-cells. It found that the "immune memory" may last for at least eight months after infection, with researchers saying the slow rate of decline in some cells required for immunity could mean it lasts longer. The study raises hopes that the protection conferred by Covid vaccines could last for years instead of an annual jab being required. Shane Crotty, a virologist at La Jolla, told The New York Times: "That amount of memory would likely prevent the vast majority of people from getting hospitalised disease, severe disease, for many years." A number of different papers have recently suggested that immunity may wane in as little as three months, raising questions about how effective any vaccine campaign may be. Last month, a study of antibodies found they fell by about a quarter in just three months – but more recent research on T-cells was far more optimistic, suggesting a response may last for months.
Scientists said the new findings were even more hopeful, as they suggest it is possible that the "immune memory" could be triggered years later. In the new study, posted ahead of a peer review as a pre-print on medRxiv, researchers took periodic measurements of the levels of antibodies as well as memory T and B-cells and other immune cells in the body. The research involved 185 Covid survivors, including 41 who were tracked for more than six months.
The T-cells – the immune component that both kills off cells that have been infected and helps B-cells make antibodies – was found to still be present at six months. Almost all the survivors developed memory B-cells that were capable of creating new antibodies if they encountered coronavirus again. The research found the longer term form of antibodies, known as immunoglobulin G (IgG) only showed "modest" declines at the six to eight month marks. Scientists have previously raised fears that those who develop only mild infections would be unlikely to have a strong immune response, making them vulnerable to repeat infections. But significantly, 92 per cent of those studied only had mild infections, never needing to be hospitalised. . . . . "
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