The question of the immunity of recovered Covid-19 people is still subject to debate within the scientific community. A recent study which was the subject of a pre-publication estimates that a part of these patients has never developed antibodies!
Antibodies linked to the inflammatory response
Many of the Covid-19 patients have had mild symptoms and have easily recovered. And yet some of these individuals would not have never developed antibodies. This conclusion is that of a British study pre-published on the medRxiv platform on June 9, 2020. As part of this study, the researchers analyzed the level of antibodies or immunoglobulin type G (IgG) in 177 patients, and this over a period of two months. In addition, these were declared positive for Covid-19 by means of a PCR test. According to the results, between 2 and 8.5% of patients have not developed any antibodies!
The study indicates that the production of antibodies is proportional to the intensity of the symptoms. In other words, patients with developed a severe infection are more likely to have developed antibodies. This would also be the case for the elderly, obese and suffering from hypertension. At the bottom of the scale, we find asymptomatic people. For researchers, the immune response could therefore be linked to the inflammatory response. It could also be that a higher viral load stimulates more inflammation and the production of antibodies.
More difficult to find a vaccine?
However, the absence of antibodies does not necessarily mean an absence of immunity. Researchers say “Limited immune responses to other antigens or transmitted by T cells”. It must be said that another study (this time German) had in April 2020 raised a possible cross immunity between colds and Sars-CoV-2 (Covid-19). It is also possible that the mild infections concerned only the cells of the mucous membranes of the respiratory tract. In this case, the antibodies would remain undetectable in the immune system overall but should be present in the stool.
The debate continues to rage since the British study contradicts a French study of May 2020, carried out jointly by the Institut Pasteur and the CHU of Strasbourg. This research indicated that 98% of patients with by Covid-19 had developed neutralizing antibodies. Incidentally, note that the three studies discussed in this article have all been published on the pre-publication platform medRxiv. Thus, these must be subject to validation by peers.
We should also mention the fact that nobody really knows what level of antibodies is ideal for good immunity and how long these same antibodies remain in the body. In any case, this lack of consensus on this subject could make it even more difficult to develop a vaccine. Indeed, a vaccine confers sterilizing immunity but does not necessarily prevent an infection of the respiratory tract. In this case, the vaccine could only make the symptoms less severe.
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