The asymptomatic become immune ?

Jean-François Cliche
The SunLes asymptomatiques deviennent-ils immunisés ?

Les asymptomatiques deviennent-ils immunisés ?

Les asymptomatiques deviennent-ils immunisés ?

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May 17, 2020 4: 00

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The asymptomatic become immune ?

SCIENCE DAILY / “My daughter of almost 13 years recently asked : is a person who is only a carrier of the virus (and therefore asymptomatic) can re-catch the COVID-19 ? Will it have the antibodies even if she never developed the disease ?”, application Joelle Fournier, Montreal.

This is a great question on which a study was just published last week in the Journal of the American Medical Association (JAMA). For three weeks, researchers have conducted serological tests, which detect antibodies, in 13 patients (including one confirmed case of COVID-19) and 25 workers in a hemodialysis unit pediatric. In the end, only three of those 38 have developed symptoms of the COVID-19 but, at the end of the study, 14 had been “séroconvertis”, that is to say that they had necessarily had the virus since they had antibodies. One of them had even had three PCR assays (which detects the genetic material of the virus and not antibodies) – negative during the study, a sign that he had a viral load very low, but it was when the same antibodies.

It is not known if these people were infected by the young patient who has tested positive in the beginning of the study, or if they have caught the coronavirus elsewhere, but the essential to answer the question of Ms. Fournier is that 11 participants of the study have become “hiv-positive” even if they have done a COVID-19 without any symptoms. And this is not particularly surprising, mind you, because we know of other cases of seroconversion in asymptomatic. In a study published in 2010 on 226 members of the nursing staff of a military hospital in Singapore, 39 had developed antibodies to the influenza AH1N1, of which 31 had shown no symptoms.

Now, the question to $ 1000 (minimum) is the following : the fact of having antibodies protects it against re-infection ? And if yes, for how long ? In the case of influenza, it is known that the antibodies prevent them from re-catching the flu — at least as long as the virus has not mutated enough to no longer be recognized by the immune system. But what is the COVID-19 ?

It is possible that the asymptomatic and do not produce as many antibodies as those that are a more serious form of the disease. Last march, a small study in china found that patients with the COVID-19 of which were in a critical state produced more antibodies than those who had a moderate form of the disease. But the sample was very small (9 patients) and high levels of antibodies are not always associated with better immunity. To follow, so.

For now, here’s what we know about the protection conferred by the antibody to the COVID-19 :

– There is currently no documented cases of re-infection. There has been this history of almost 300 patients from south korea who had tested positive several weeks after complete remission, but it turned out that the tests had detected fragments of a virus, not live virus or contagious. At the time of writing these lines, one approach of the 4.5 million confirmed cases and 1.6 million healing on a global scale since the beginning of the pandemic. The absence of re-infection confirmed among them is not, in itself, a formal proof, but it shows that we had a lot of opportunities to find and that if it is not happened despite monitoring quite tight (even if it varies from one country to the other), this suggests that re-infection, if they exist, are very rare.

– There has not been any studies that have attempted to re-infect humans healed, but there is one, done on macaques, who found that monkeys don’t re-catch not the disease once cured. It is a very good sign, but it is however a very small study (4 macaques in total) that has not yet been reviewed or published by a scientific journal, then it should be considered with caution.

– Ignoring for the moment how long the immunity will last. The pandemic is not old as 5 to 6 months, then it is impossible to know with certainty whether the body will remain protected for 1 or 2 years or even more. It will have to wait to be fixed. In the case of the nearest known parent of the COVID-19, the virus of severe acute respiratory syndrome (SARS), the antibody remained in high concentration in the blood for 4 to 5 months after the healing, we read in a “round-up” on immunity published last Monday in the JAMA. Nearly 90% of the patients still had antibodies at the end of two years, and about half after three years. However, it is known that reinfection are possible for at least three of the four “human coronaviruses” (circulating in the human species since time immemorial and which are usually just colds very mild), or because the immunity they induce is of short duration or because people may be exposed to genetic variants different of these viruses.

Then we will have to wait again before being certain, but for the moment, everything indicates that the asymptomatic form of the antibody, and that the “séroconvertis” are beautiful and well protected against re-infection.

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You have to ask questions about the world that surrounds you ? They concern physics, biology or any other discipline, our journalist will be happy to answer them. To our eyes, there is no “silly question”, no matter “too small” to be interesting ! Then write to us at : jfcliche@lesoleil.com.

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