Those recovered from Covid begin to be a fair number (almost 230,000 since the beginning of the epidemic). They are also joined by those who with the serological test discovered that they had come into contact with Sars-CoV-2 (from asymptomatic or symptomatic) after the test reported the positivity of the immunoglobine IgG, our body’s memory antibodies to infection. But all these people if for various reasons will come into contact with a positive for the new coronavirus will they have to undergo fiduciary isolation and possibly a tampon?
The fact of having been infected and having had the double negative swab that indicates healing four months ago does not exclude that the subject may have a new infection today, test positive for the swab, and still be able to transmit the virus immediately puts in clear Pierangelo Clerici, president of the Italian Clinical Microbiologists Association and of the Italian Federation of Laboratory Scientific Societies. Therefore even for those recovered from Covid it is right to face quarantine (again). Furthermore, those who get sick and have not undergone a serological test will not be able to know the possible presence of neutralizing antibodies, or protective ones.
Immunity and reinfection
Then there are those who, undergoing serological tests, discovered that they have IgG antibodies in the body. In theory these subjects could feel immune but in truth there are still many uncertainties about the real activity of these antibodies.. At the moment in fact, there is no certainty that positive serological tests are indicative of protective immunity against the virus. And above all we do not know its permanence in the organism. The whole scientific world is studying what antibodies are and their necessary level for protection from reinfection. We don’t know if the antibodies are really protective or how long they last. Until then everyone will have to adapt to the protocol that provides for isolation if you come in contact with positive people simplifies Clerici. Although i cases of reinfection documented can be counted on the fingers of one hand (with the limit that no antibody tests have been carried out so it is not known if the subjects had developed the antibodies) to date the possibility of re-ill-illing or even just testing positive consequently be contagious. The fact that he developed antibodies two months ago is not certain of having kept them today. For all these reasons, even those who have been sick with Covid and those who tested positive for IgG immunoglonins will have to keep the same precautions as the rest of the population: wear a mask, wash your hands often, maintain social distancing.
To study immunity, large-scale studies are needed
For now, studies on the duration of antibodies have given mixed answers
. In some cases they seem to disappear after three months after infection, in others last longer. To know how long immunity lasts and to make a correct statistical evaluation we have to wait population studies with important numbers – Clerici clarifies – and I mean about 50-100 thousand people who have been sick and that every week or at most two are subjected to serological tests to check if they keep the antibodies. These are studies that normally last at least five years because time plays a key role. However, I think that by the end of the year we will begin to have clearer answers thanks to the numerous independent studies launched around the world that all together will be able to provide important numbers.
The duration of immunological memory
Finally, let’s not forget that the immune response changes from person to person as seen in the studies done so far. And this applies to all infectious diseases. On all vaccinations there is also a percentage of 3-5% of so-called no-responders: people who, despite vaccination, develop few or even no antibodies and immunity tends to disappear rapidly. The important concept is that the immunological memory must develop, the one that really saves us – Clerici concludes -. Anyone who gets sick or is vaccinated against a pathology will no longer get sick thanks to the antibodies produced by the stimulation of the immunological memory. The subject can reinfect, but does not get sick because the T lymphocytes, holders of the immunological memory, stimulate the production of antibodies that block the virus. On Covid we have yet to find out if this immunological memory is present and in what quantity, how long it lasts and how effective it can be.
October 7, 2020 (change October 7, 2020 | 13:11)
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