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between 2 and 8% of infected patients never develop antibodies

The immunity conferred by a coronavirus infection continues to divide scientists. Are you really protected after being sick and how long does this immunity last? A new study provides some answers.

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If you have been infected with coronavirus with weak symptoms, do not rejoice too quickly: you may not be immune. This is what emerges from a new study (not yet published) published on the site medRxiv. The latter analyzed the rate ofantibody IgG (neutralizing antibodies) in 177 patients diagnosed positive for Covid-19 with a Review PCR, up to 60 days after the Review. According to the results, between 2% and 8.5% of patients never develop these famous antibodies – proportion assessed according to the duration follow-up, variable from one patient to another.

The sicker you are, the more likely you are to develop antibodies

Antibody production is more likely the stronger the symptoms. People who have developed severe infections, the elderly, obese or those suffering fromhypertension are therefore much more likely to develop antibodies than asymptotic people. " This could be due to the fact that the immune response is paired with the inflammatory response, or that an viral load higher stimulates moreinflammation and the production of antibodies "Suggest the researchers.

The absence of specific antibodies to SARS-CoV-2 does not mean that you are not immune. " It is possible that these patients (who remain seronegative, editor's note) have had limited immune responses to others antigens or transmitted by T cells "Say the authors. A previous study, for example, suggested that there would be cross-immunity between colds and Sars-CoV-2. Another possible explanation is that mild infections may have been limited to the cells of mucous membranes respiratory tract. In this case, the antibodies are present in the secretions but undetectable in the immune system overall, they explain.

An ineffective vaccine to prevent a new infection?

This study contradicts that of the CHU of Strasbourg and the Pasteur Institute published in May (read below). The latter indicated that 98% of infected patients had developed neutralizing antibodies, including those who had minor forms of the disease. In addition, it is not known what level of antibodies is necessary to be immunized, nor how long they persist in the body, because we still lack the necessary perspective. The figures presented here seem to show a relatively stable rate up to two months after infection, but other studies on the 2003 Sars-Cov have shown that IgG is detected in approximately 50% of patients four years after infection.

The continuing vagueness around this issue could complicate the vaccine development. The latter being injected into the body, it confers immunity called "sterilizing" but does not necessarily prevent infection of the respiratory tract. This means that a vaccinated person could become locally infected and continue to spread the virus. virus coughing or talking. In this case vaccination should however limit the severity of the symptoms, which is all the same essential to avoid congestion in hospitals like the one we experienced in March.

Coronavirus: weakly affected patients have developed antibodies

AFP-Relaxnews article published on 05/30/2020

Encouraging, this study showing that almost all of a group of caregivers, weakly affected by the coronavirus, developed protective antibodies still present 28 days after the onset of symptoms. How long will this immunity last?

An "overwhelming majority" of patients with a minor form of Covid-19 develop antibodies which could then immunize "For several weeks" against the disease, according to a study by the Strasbourg University Hospital and the Pasteur Institute, detailed on the site MedRxiv.

These results are "encouraging" since little is known about the mechanisms of immunity against the new coronavirus, especially in people with minor forms of the disease. " It was known that people with severe forms of the disease developed antibodies within 15 days of the onset of the signs. We now know that this is also true for those who make minor forms, even if the antibody levels are probably lower "Explains in a communicated one of the study's authors, Arnaud Fontanet, head of the Global Health department at the Pasteur Institute.

" Our study shows that the levels antibody are, in most cases, compatible with protection against re-infection with Sars-CoV-2, at least up to 40 days after the onset of signs "Adds Olivier Schwartz, head of the Virus and immunity unit at Pasteur. According to him, " the objective now is to assess the persistence of the antibody response and its neutralization capacity over the long term Of the virus.

A " good news "To develop a future vaccine

The study, the results of which were published on Saturday and to which Pasteur communicated on Tuesday, was carried out on 160 patients, members of the hospital staff of the two sites of the university hospitals of Strasbourg. They were all affected by minor forms of Covid-19.

Serological tests (which aim to detect signs of a past infection after the fact) have shown that almost all of these people (153 or 159 out of 160 depending on the type of Review) developed antibodies within 15 days. the start of the infection. Another Review was used to determine whether these antibodies had the capacity to neutralize the virus. Verdict: 28 days after the onset of symptoms, 98% of patients had developed these "neutralizing antibodies".

" These results are also good news for future vaccine strategies ", Underlines Pr Samira Fafi-Kremer, head of the virology service of the University hospitals of Strasbourg and first author of the study, also quoted in the press release.