The problem of the immunity of recovered Covid-19 is still subject to debate in the scientific community. A recent pre-published study estimates that some of these patients have 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 never have 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 in 177 patients, and this over a period of two months. They were also found positive for Covid-19 using 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 who have developed a severe infection are more likely to have developed antibodies. This would also be the case for the elderly, obese and people with hypertension. At the bottom of the scale, we find asymptomatic people. For researchers, the immune response could therefore be linked to the inflammatory response. A higher viral load may also stimulate inflammation and the production of antibodies.
More difficult to find a vaccine.
On the other hand, the absence of antibodies does not necessarily mean a lack of immunity. Researchers say, “immune responses limited to other antigens or transmitted by T cells”. It must be said that another study (this time German) had in April 2020 evoked 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 overall immune system 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 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, the latter must be subject to peer validation.
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 event, this lack of consensus on this matter could make the development of a vaccine even more difficult. 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.