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THE natural immunity towards the new coronavirus recovery, not immunity artificially induced by vaccination, may take at least six months, depending on two new studies by American scientists.
The exact duration of natural immunity (without a vaccine) can be difficult to predict because scientists don’t yet know exactly what levels of different cells of the immune system are necessary to protect against the new virus. However, both new and other studies show that even a relatively small number of antibodies or T and B cells is sufficient in most people to protect them for a long time after an injury. COVID-19 contagion.
In the first study, their researchers Howard Hughes Medical Institute and his Rockefeller university from New York, who made the relevant pre-publication in bioRxiv (not yet published in a scientific journal), collected blood samples from 149 patients with Covid-19.
It was found that one month after infection, all patients had antibodies against the SARS-CoV-2 coronavirus. Six months after the initial infection, these antibodies were even stronger and better at fighting the virus.
The findings, according to the scientists, show that immune system Patients now appear to be able to treat the coronavirus if they are exposed to it again. “The very good news is that infected people are very unlikely to get sick again for at least the next six months,” said Rockefeller immunologist Dr. Michel Nussenweig.
The researchers also said that the presence of antibodies in the many patients who recovered was an encouraging sign for the human response to vaccines.
A second study, also at bioRxiv, led by the virologist Shane Crotch from the La Jolla Institute of Immunology in California, which analyzed blood samples over a period of months from 185 patients aged 19 to 81 years with Covid-19, came to the even more encouraging conclusion that the body’s immune memory and therefore Therefore, the presence of the corresponding antibodies in the body for those who have had the disease, lasts at least six months and, in some cases, several years.
Two types of T cells (CD4 + T and CD8 + T) that kill other infected cells show a relatively slow decline in the body (to 50% after three to five months), while memory B cells produce more antibodies. on the way, if necessary. , show an unexpected increase over time, as it is more after six months than one month after the initial infection.
The study shows that eight months after the initial infection, most people who have already recovered still have enough antibodies to get rid of the coronavirus and prevent a new infection. The rate of decline in antibodies appears relatively slow, according to the researchers, so in at least some cases, natural immunity can last a long time, according to the New York Times.
“The number of memory cells is likely to prevent the vast majority of people from getting seriously ill and being treated for coronavirus for many years,” said Dr. Crotti.
This assessment brings an air of optimism, in contrast to the pessimism that had spread in recent times. pessimistic british study according to which anti-coronavirus antibodies decrease significantly within a few months. American scientists hope that immunity to the virus is not short-lived and that this will have a positive effect on vaccines when they start, as they probably don’t need to be repeated at regular intervals.
These findings are consistent with those of other encouraging studies, showing that those who have recovered from Covid-19 have strong physical immunity. “All of these studies point to more or less the same picture, that once a person goes through the critical first weeks of infection, the rest of their immune response seems pretty conventional,” said University of Arizona immunologist Dipta Batatsaria.
“Exciting news, what should have happened,” said the Japanese-born immunologist. Akiko Ivasaki from Yale University.
However, as the new study showed, a small percentage of patients do not have lasting physical immunity after recovery. In this case, according to Canadian immunologist Jennifer Gomerman University of Toronto, The vaccines are expected to fill the gap in the immune response.
