Remdesivir, antibodies and immunity to coronavirus: research update

Audio 04:03

By: Nicolas Rocca Follow

Each week, RFI takes stock of scientific advances in the fight against the Covid-19 pandemic. And this week, a study that does not speak of hydroxychloroquine but of the new antiviral, remdesivir.

Publicity

At the end of April, the Gilead laboratory presented remdesivir as having very effective effects against Covid-19. A month later, the very serious New England Journal of Medicine published a study with results that can be described as encouraging on the molecule. This trial includes more than 1,000 patients, mainly from the United States but also from a few European countries. The model of the trial is fairly standard: the patients are divided into two groups, one receiving doses of remdesivir and the other a placebo.

"  Overall, there is only a reduction in clinical healing time by 32%, and there is no significant efficacy on mortality , points out Gilles Pialoux, head of the infectious diseases department of Tenon hospital in Paris. But there is a benefit in unventilated oxygen patients, it is a large population that we have seen in the departments. The benefit in these patients is 42% reduction in healing time and 5 times less death.  "

The study, despite promising conclusions, did not come to an end, so that all patients could receive remdesivir.

However, a Chinese essay published in the Lancet tempers optimism about this treatment, demonstrating an effect on the healing time, already noted elsewhere, and which displays a limited effect. What remains certain is that concerning the most serious forms, there is no certainty as to the effectiveness of this anti-viral. It is rather towards other treatments such as tocilizumab that research seems to be turning to.

Memory immunity

It was a central question around this virus and the management of this epidemic: is an infected patient then protected? The Institut Pasteur and the University Hospital and Research Center of Strasbourg provide some answers in a study . 160 caregivers tested positive thanks to a PCR test, underwent serological tests for six weeks, in order to detect their immune response to the virus. All patients, with the notable exception of one, developed antibodies after six weeks.

But it was also necessary to test the quality of these antibodies, to analyze their blocking action against the virus, what is called their neutralizing capacity, but also their quantity. In this area too, the study provides reassuring elements.  

"  We took measurements of people who had antibodies with neutralizing activity, we saw that this rate increased over time from about 60-70% from D13, up to 98% of people , explains Olivier Schwartz, head of the virus and immunity unit at the Institut Pasteur and signatory of the study. The amount varies from person to person, but this is encouraging because it shows that the immune system is able to produce antibodies with neutralizing activity.  "

Antibodies effective in almost all patients, all symptomatic, with an amount that increases over time. However, two questions remain unanswered: asymptomatic patients, by nature more difficult to find and therefore to test, do they also produce antibodies?

And above all, how long does this immunity last? Impossible to determine for the moment, if it is about a model similar to a flu with a protection which disappears after a few months or if an infected person is protected for several years. For this, by definition, a longer-term study must be carried out.

Our selection on the coronavirus

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• Our series  :
→ “  The response, country by country  ”
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• Each evening, find the State of the world and Africa facing the pandemic

• See also the files of RFI Savoirs on the Covid-19:
→  Birth of a pandemic
→  Everyday life put to the test
→  The history of epidemics
→  Science facing the Covid-19
→  The geopolitical consequences

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