a vaccine, a hope and questions

Finally good news. As the coronavirus Sras-Cov-2 killed more than 1.2 million, including 42,000 in France, the announcement of a vaccine “90% effective” of the American laboratory Pfizer and its German partner BioNTech gives serious hope to control the epidemic.

“This is the first time we have data showing the effectiveness of a coronavirus vaccine,” confirms Odile Launay, an infectious disease specialist at Cochin hospital, Paris, and a member of the Covid-19 vaccine committee. However, as the announcement was made in a press release and not in a scientific publication, many questions remain.

What we do know is that this vaccine uses a new technology, messenger RNA, never used before for humans. For a long time, “We had a somewhat empirical view of things: we injected an attenuated or deactivated piece of virus to cause a defensive reaction in the body”, recalls Jean-Daniel Lelièvre, head of the infectious diseases department of the Henri-Mondor hospital in Créteil (Val-de-Marne).

Then we got interested “An envelope protein called the Spike protein, which works as a kind of key that allows the virus to enter our cells, and we started using it in vaccines.”

Limited samples

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

→ EXPLANATION. Covid vaccine, the battle for doses

But what do we know of its real effectiveness? To obtain its results, Pfizer and BioNTech have already carried out clinical trials on limited samples in phases 1 and 2. Since July they have tested the vaccine on 43,500 volunteers, chosen from areas of active viral 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, coronavirus infection cases are reduced by “More than 90%” in vaccinated people.

“To grant a marketing authorization, decrypts Jean-Daniel Lelièvre, the 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 subsequently denied,” adds Jean-Daniel Lelièvre.

What side effects?

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

So, with 90% efficacy measured seven days after the second and last dose of vaccine is injected, 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 enough to be able to detect possible side effects.

Some technical constraints remain to be solved, such as vaccine storage, which requires freezers at – 70 ° C. “But it’s not insurmountable, esteem Jean-Daniel Lelièvre, the Ebola vaccine requires the same conditions and we have successfully vaccinated in Africa. “ In short, suit Jean-Daniel Lelièvre, “Hopefully, 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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The word: “vaccine”

The word derives from vaccine, in turn from the Latin vaccinus (“which belongs to the cow”). The beginnings of vaccination date back to 1796, when Edward Jenner, an English country doctor, practiced by scarification the first inoculation of the vaccine, which has the property of preserving smallpox and collected in pustules on the udders of cows.

In the mid-nineteenth^is century, arm-to-arm vaccination was abandoned and the virus grown in the laboratory. In 1885 Louis Pasteur entrusted Dr. Grancher with the task of inoculating the treatment to a 9-year-old boy, Joseph Meister, who came from Alsace and had been bitten 14 times by a rabid dog, who became the first human being vaccinated.