A vaccine, a hope and questions

Good news at last. While the Sras-Cov-2 coronavirus has killed more than 1.2 million, including 42,000 in France, the announcement of a vaccine “90% effective” by the American laboratory Pfizer and its German partner BioNTech raises serious hopes of controlling the epidemic. “This is the first time that we have data showing the effectiveness of a vaccine against the coronavirus”, confirms Odile Launay, infectious disease specialist at Cochin hospital, in Paris, and member of the Covid-19 vaccine committee. However, the announcement having been made by press release and not in a scientific publication, many questions remain.

What we do know is that this vaccine uses a new technology, that of messenger RNA, never before used for humans. For a long time, “We had a somewhat empirical view of things: we injected a piece of attenuated or deactivated virus to provoke a defensive reaction in the body”, recalls Jean-Daniel Lelièvre, head of the infectious diseases department at Henri-Mondor hospital in Créteil (Val-de-Marne). Then we got interested in “An envelope protein called the Spike protein, which functions as a kind of key allowing the virus to enter our cells, and we have started to use it in vaccines”.

Now, he continues, with this new messenger RNA technology, “It’s about injecting genetic material that tells the body to produce antibodies against this protein. ” A technique, resumes Odile Launay, which “Has the advantage of allowing vaccines that are easier to produce”.

But what do we know about its real effectiveness? To obtain its results, Pfizer and BioNTech have already carried out clinical trials on limited samples in phase 1 and 2. From July, they tested the vaccine on 43,500 volunteers, chosen from areas of active virus circulation and divided into two groups, one receiving the vaccine, the other a placebo. At the end of the trial, 94 infections were recorded. According to preliminary results, cases of coronavirus infection are reduced by “More than 90%” in vaccinated people. “To give a marketing authorization, decrypts Jean-Daniel Lelièvre, health authorities are asking for an efficacy rate of 50%, with at least 164 infections. There, we certainly have fewer infections, but the efficiency, at 90%, is very high so it is very promising. ” All this remains to be confirmed with the final results of phase 3. But “I don’t think they would have taken the risk of announcing these results if they were to be subsequently denied”, adds Jean-Daniel Lelièvre.

However, a number of outstanding questions remain. ” First of all, Odile Launay analysis, In the absence of a study publication, it is not known which form of infection the vaccine protects against. In particular, does it prevent the asymptomatic form, which is also contagious? ” Furthermore, “We would like to know if this vaccine can protect people at risk as well, especially the elderly”.

Then, with 90% efficacy measured seven days after the injection of the second and last dose of the vaccine, or 28 days after the first, scientists wonder how long this efficacy can last – ideally, the vaccine protects for at least a year. Finally, complete Odile Launay, the most important question is that of security ”, the 28-day period is not sufficient to be able to detect possible side effects.

Some technical constraints remain to be resolved, such as that of vaccine storage, which requires freezers at – 70 ° C. “But it’s not insurmountable, believes Jean-Daniel Lelièvre, the Ebola vaccine requires the same conditions and we have successfully vaccinated in Africa. “ In short, complete Jean-Daniel Lelièvre, “If all goes well, we should, wherever doses have been ordered, have a vaccine available in early 2021.” In the European Union, where the authorities want to order 300 million doses, the first vaccinations could take place “In the first quarter of next year (…), being optimistic ”, hopes Andrea Ammon, director of the European Center for Disease Control (ECDC).


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