"The efficacy of the fourth injection against the Omicron strain is low": here is the title of the press release published on Monday, January 17, by the Sheba hospital, near Tel Aviv, to present the preliminary results of "the first study of its kind in the world". Since the start of the vaccination campaign at the end of December 2020, Israel – which was one of the first countries to massively vaccinate its 9.2 million inhabitants – has been a life-size laboratory on the effectiveness of vaccines against Covid. -19, observed by the other countries which started their respective campaigns later.

Faced like many countries with the threat of the Omicron variant, the Jewish State decided on December 14 to conduct a study, entrusted to the Sheba Medical Center, "to examine the effects of a 4th 'booster' vaccine on the level of antibodies in 200 volunteers (finally 274, editor's note)".

The study first examined over a week – the clinical trial is to extend over six months – the level of increase in antibodies after a fourth vaccine from two different companies (154 caregivers with Pfizer or 120 volunteers with Moderna), compared to a control group that did not receive a fourth dose. Result: "The antibodies (of participants who received a 4th dose, editor's note) were multiplied by five, which indicates that the vaccine works and offers protection against serious complications", indicated the hospital to the press.

But on Monday, three weeks after the start of clinical trials, Professor Gili Regev-Yochay, who is leading the study, said in the Sheba Hospital statement that if the administration of these fourth doses indeed allows "d 'raise the level of antibodies', it only 'offers partial defense against the virus'. “The Pfizer and Moderna vaccines, which were more effective against the other variants, offer less protection against Omicron”, also added the infectious disease specialist.

“The first feedback from Israel is not very encouraging for recommending the fourth dose of vaccine”, admits epidemiologist Antoine Flahault, contacted by France 24. And to specify: “The fourth dose is very debated on the plan scientific for the moment, including in Israel, in particular for reasons of acceptability. The population was much more reluctant there than for the third dose (nearly half of the population of the Jewish State received a third injection, Ed. )."

A helpful reminder for at-risk populations

Regarding the fourth injection, Israel prioritized, in December, the immunocompromised then the elderly over 60 and caregivers. More than 537,000 Israelis have now received a fourth injection, according to the latest Health Ministry data. And this seems to be a good choice to strengthen the immunity of these audiences and protect them from serious forms. “Although the vaccine we have today does not offer optimal protection against infection with the Omicron strain,” notes Gili Regev-Yochay, “it is correct to continue the vaccination campaign for populations at risk. "

For the general population, on the other hand, a vaccine originally developed to fight the Wuhan strain does not seem to be the ideal solution to deal with the Omicron variant. "We expect two things from a vaccine: humoral efficacy and cell-mediated efficacy", explains Antoine Flahault. "The first concerns the level of antibodies, the first dam of protection of the vaccine. The latter, even if it is effective, is not very convincing today vis-à-vis the new variants (given that Omicron presents a vaccine escape, Editor's note) and we can probably not expect the fourth dose to make a big difference. a very relevant immunity."

New vaccines in spring and summer

Several pharmaceutical groups indicated, at the end of November, that they were working on a new version of the anti-Covid-19 vaccine which, this time, would be more resistant against the Omicron variant.

At the beginning of December, Pfizer and BioNTech specified, in a press release, that they plan to make this new vaccine available "by March in the event that an adaptation is necessary to increase the level and duration of protection".

At the end of December, it was the Moderna company which, through its vice-president, declared on BFM Business that the laboratory was aiming to market its new serum "in the second quarter, around the summer" 2022.

"It's very good that the laboratories are working on these questions, but we must not lose sight of the fact that the decisions must be taken by independent public bodies, for example the WHO and its expert committees", recalls Antoine Flahault.

Putting the UN organization back at the center of decisions, as is done for the flu vaccine, would ultimately seem like a good solution for the epidemiologist: "The composition of the flu vaccine is decided each year at a meeting of the WHO - in February for the northern hemisphere, in September for the southern hemisphere - then recommended for all vaccine manufacturers on the planet. Perhaps one day the UN organization will recommend the composition of a vaccine against coronavirus, but we're not there yet."

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