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I study
In the first round of testing, in late June and early July, about 60 out of 1,000 people had detectable antibodies. But in the last batch of tests in September, only 44 out of 1,000 people tested positive. The fall was greater in those over 65, compared to younger age groups, and in people without symptoms, compared to those with symptomatic disease. The number of healthcare workers with antibodies remained relatively high, which the researchers said could be due to regular exposure to the virus. Some scholars comment on the results with alarm for fear of short-term immunity that would put you at risk of contracting the virus multiple times.
Other confirmations of short immunity
It is not the first time that a study has found this: it had written King’s College from London where it was seen that the level of antibodies reaches its peak after about three weeks from the onset of symptoms and then gradually decrease. The study had monitored how, three months after infection, only 17% of those who had contracted the virus maintained the same power of immune response, destined to be reduced in some cases until it was no longer detectable.
Other research published in Nature had reached the same conclusions, showing that levels of protective antibodies decrease by more than 70% in convalescence and in some subjects they are no longer detectable. It is true that the other coronaviruses in circulation are seasonal and do not offer lasting protection, but it is also true that the cousin of SARS-CoV-2, the SARS virus, on the other hand, causes the body to develop defenses that presumably last a few years (the virus, by, disappeared and the studies on it are not complete).
normal to decrease
Scholars still have no certainties how exactly the antibodies will protect us from new infections, but not everyone is pessimistic with respect to the results of these studies because, to some extent, normal for the antibodies to decrease after healing from an infection. Antibodies drop to basic levels not detectable by serological tests commonly used. For example, people with mild or no symptoms may have produced fewer antibodies than those with severe disease, but even a small decrease in the amount of antibodies can cause their levels to drop below the detection limit. We are talking about the antibodies that are also sought in Italy with serological tests: they are IgM (Immunoglobulin M), which occur within about 7 days from the onset of symptoms and allow to confirm the diagnosis of infection, and IgG (Immunoglobulin G), produced after about 14 days, which are our immune memory, tell us that in the past we have come into contact with the virus. Therefore, if it is normal for the antibodies to decrease, it is also normal low levels of antibodies can still produce a rapid response of the immune system in case of re-exposure to the virus.
Some people don’t develop them
It is also true that some people (often those with a mild infection) do not develop enough long-lasting antibodies to mount an effective response. declares the doctor Angela Rasmussen, virologist of the University of Colombia -. Bottom line: the implications for long-term immunity are unclear. To be more certain about the duration of protection we only need to continue with epidemiological studies and repeat serological tests for the detection of antibodies with a fixed term, for example every three months for those who tested positive for IgG.
There are also T cells
But there is other active parts of the immune system, such as T cells, that our tests currently do not detect and that they can play a role by directly killing infected host cells and calling in other immune cells to help. A Swedish study, published in the journal Cell in August, he discovered that about twice as many people developed T-cell immunity versus those for which we can detect antibodies with serological tests. Probably, therefore, more subjects in the population developed immunity to SARS-CoV-2 compared to what antibody tests suggest, even if they are of different types. In general, the elimination of a virus in the first encounter is not carried out by antibodies, but by T cells. T cells recognize different parts of the virus than antibodies and are essential for the memory of the infection.
Vaccine fears
We still have no certainties therefore, on how long the protection against the virus lasts once cured and on which agents of the immune system are most effective for protective memory. What we know that in some cases reinfection is possible, although it is a very rare occurrence (we talked about that who, ed).
However, concerns are limited regarding possible vaccines. the vaccine could overcome the problem disintegration of antibodies: science, in this case, may be more efficient than nature, they write in New York Times Akiko Iwasaki and Ruslan Medzhitov, professors of immunobiology at Yale University. A vaccine works by mimicking a natural infection, generating memory T and B cells that can then provide a lasting protection vaccinated people. The beauty of vaccines is one of their great advantages over our body’s natural reaction to infection – the two experts write – that their antigens can be designed to target the immune response on the Achilles heel of a virus (whatever it is ). . Another advantage is that vaccines allow different types and different doses of so-called “adjuvants” (agents that mimic infection and help restart the immune response) that can help strengthen and lengthen immune responses.
October 28, 2020 (change October 28, 2020 | 12:14)
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