How long does the immunity against Covid-19 after passing the illness? Understanding the immune memory of SARS-CoV-2 is essential to improve diagnostics and vaccines, and to assess the likely future course of the pandemic. Therefore, since this health crisis began, many research groups have tried to answer this question, with results, in some cases, very encouraging and in others, less.
The latest published work on the subject, conducted by researchers at the La Jolla Institute of Immunology in California, suggests that immunity could last for years. Eight months after infection, most people who have recovered from Covid-19 still have enough immune cells to defend themselves against the virus and prevent the disease, new data shows. A slow, short-term rate of decline suggests that these cells may persist in the body for a long time.
The research, whose prepublication can be consulted at bioRxivhas not yet been peer-reviewed or published in a scientific journal, although its authors claim that it is the first to trace the immune response to a virus in such detail.
To do this, they analyzed multiple compartments of circulating immune memory for SARS-CoV-2 in 185 cases of Covid-19, most mild. Most of the participants provided a blood sample at a single time, between 6 and 240 days after the onset of symptoms. A total of 41 samples were taken more than six months after the onset of symptoms. Thirty-eight people provided longitudinal blood samples over several months.
The team tracked down four components of the immune system: antibodies, B cells that produce more antibodies as needed; Y two types of T cells that kill other infected cells. The idea was to build a picture of the immune response over time by looking at its components.
The researchers found that the antibodies were durable, with modest reductions six to eight months after infection, although there were notable differences in levels between participants. T cells showed only mild and slow deterioration in the body, while B cells increased in number, an unexpected finding that the researchers cannot fully explain.
That amount of memory probably prevent the vast majority of people from getting a serious illness that needs hospitalization for many years, ”Shane Crotty, a virologist at the La Jolla Institute of Immunology who co-led the new study, told the New York Times.
This research squares with another recent finding that revealed that survivors of SARS, caused by another coronavirus, still carry certain important immune cells 17 years after recovering.
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