Fourth vaccine dose: is Israel going too fast?

It reigns like an air of déjà vu in Israel. A pioneer in booster vaccination, the country considered to be the first human-sized laboratory of the Covid – will again be observed very closely by Europe and the United States. Israeli Prime Minister Naftali Bennett announced on Tuesday that most of 50 years, immunocompromised people and caregivers can now benefit from a fourth dose of anti-Covid vaccine, considering that it was “excellent news that will help us get through the Omicron wave that is sweeping the world.”

Problem, the Israeli government has not based its decision on any scientific study. Only its committee of experts gave its approval for the start of the campaign. Sheba Medical Center, located in Ramat Gan, Israel, is currently researching the fourth dose with 164 volunteers who received a fourth dose, but no preliminary results have yet been published. The World Health Organization (WHO) even warned, this Wednesday, against the illusion that it would be enough to administer booster doses to get out of the Covid pandemic – 19. “No country will be able to get out of the pandemic with booster doses and the reminders are not a green light to celebrate as we had planned”, declared Tedros Adhanom Ghebreyesus, the director general of the institution.

“With all the medical procedures that we do in the world, there is always a certain degree of risk”, concedes Zvika Granot, Israeli immunologist at the Hebrew University of Jerusalem . But “the initiative to start a fourth dose campaign is not based on any clinical trial. There is no guarantee that it is safe, although I presume there is not a big risk, even a greater risk than previous injections “, continues the specialist.

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Same strategy as during the summer

Last August, Israel was already the first country to open the third dose to its citizens over 60 year . Already at the time, no study had been published on the subject. Only the existence of a drop in the effectiveness of the two doses of the vaccine had prompted the Israeli government to step up. If the fourth dose for those less than 40 years is not yet relevant in Israel, we can estimate that it could happen quickly.

One month after the opening of the recall to over 50 years in the country, the entire adult population became eligible. “There are risks of myocarditis, already noted with the third dose of Moderna for less than 19 years, which could affect younger subjects. A 50 years, the incidence of myocarditis is weaker “, notes Jean-Daniel Lelièvre, member of the Haute Autorité de Santé and head of the clinical immunology department at CHU Henri-Mondor in Créteil.

For Guillaume Lefevre, immunologist at Lille University Hospital and author of a study demonstrating the effectiveness of a third dose published last July, “there is no reason not to increase the number of reminders”. “It does not exhaust the immune system and it maintains the immune response. It is tiny compared to all of our immune defenses. It only boosts a very specific response to SARS Covid. Do it every week or every month would make no sense. But repeating them every six months to optimize the immune response, there is consensus, “he defends.

Omicron is changing the game

With the arrival of Omicron, whose high number of mutations would lead to a drop in antibodies, is once again asking the question of a new version of the vaccine suitable for variants . “Continuing to vaccinate with the original Wuhan strain is no longer necessarily relevant, all the more so with the arrival of Omicron,” said Jean-Daniel Lelièvre.

Moderna and Pfizer have already announced that they are working on a vaccine suitable for this new variant. “It’s going a little too fast. As soon as we have finished analyzing the variants, we have already moved on to the next one,” admits Guillaume Lefevre. However, the American laboratories had promised the same thing for the Delta variant, without a new serum really seeing the light of day.

In France, the government is counting for the moment on the acceleration of the recall campaign, opened since 27 November to the entire adult population. Auditioned in the Senate on December 8, the President of the Scientific Council Jean-François Delfraissy had estimated “that it is possible that at some point we need a fourth dose”, while specifying that he did not know “how much long will the reminder last.

In France, only immunocompromised people can benefit from a 4th dose. “Immunocompromised people have a very high risk of developing a severe form of Covid – 01. They are more likely to suffer from the disease than from possible side effects of the vaccine. ‘It is very important to have the best protection, ”Zvika Granot said. It remains to be seen what will be the benefit of a fourth dose in Israel, which, as often, foreshadows what will happen next.