This study conducted by King’s College London was carried out on 90 patients. The goal was to find out a little more about potential immunity. Conclusion: the former Covid-19 patients have made antibodies well. Antibodies effective for three weeks, strong fighters of the virus. Cannot be re-infected during this period.
But this study shows that after these three weeks, the antibodies decline and are much less protective of the virus.
In some patients, the antibodies would no longer be effective at all in as little as three months. According to the blood samples taken, 60% of those infected have effective antibodies one month after their infection, but after three months, this drops to 17%. For some patients, the antibodies are no longer even detectable.
This study is a blow for the defenders of collective immunity but it must be put into perspective. ” Antibodies are just one aspect of immunity acquired from contamination, explains Bruno Megarbane, head of the resuscitation department at Lariboisière hospital. There is cellular immunity. Even if the blood level of antibodies decreases, having memory cells makes it possible to quickly generate antibodies if you are re-exposed. “The doctor adds” that we cannot comment on the risk of re-developing the disease a second time but by analogy with other coronaviruses, it is likely that this immunity will not be prolonged ».
Collective immunity is, for the moment, only 6 to 7% in France. To be effective, it must reach at least 70% of the population
This study also confirms that the severity of the virus also has consequences on the immune response. The weaker the symptoms, the less the antibodies resist. Patients suffering for several weeks, whether from fever or respiratory problems, will be better protected than those with mild symptoms Similar studies conducted in Germany and Spain have reached the same conclusions.
These immunity studies can guide future vaccines
These vaccines should be more powerful than natural protection alone. Their strength will also have to be more durable at the risk of having to ” reinject the vaccine regularly ” This is one of the conclusions of the researchers who carried out this study.
The American biotech firm Moderna has announced that it has entered the final phase of its clinical trials of its vaccine against Covid-19 from July 27. 30,000 people will participate in this last decisive phase. Half will receive a dose of 100 micrograms and the other half will receive a placebo.
The primary objective of this trial is to find out if the vaccine is safe and prevents SARS-CoV-2 infection. The study will last two years and the biotechnology startup warns: the vaccine will be considered a success even if patients develop symptoms. Most importantly, it prevents serious cases of Covid-19.
The experimental vaccine had triggered the production of antibodies to SARS-CoV-2 in the 45 participants. Not all had received the same dose of vaccine and it was found that the antibody levels were higher with the higher doses. Regarding this third phase, if the formula chosen for the tests proved effective, Moderna planned to be able to produce 500 million doses per year, and ” possibly up to 1 billion ».
Rfi
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