Since the start of the covid 19 epidemic, we have wondered about the duration of the immunity obtained after an infection, which is supposed to protect us durably against a new infection by the same virus. One of the reasons for these questions is the possibility, for certain cold viruses (close relatives of SARS-CoV-2, but much less pathogenic) to infect us every winter as if our immunity quickly became ineffective. If the same were true for SARS-CoV-2, any individual infected a first time, having been ill or remained asymptomatic, could be infected again after a few months or years, his immune system not having preserved the memory. of the initial infection.
While we now have vaccines with demonstrated efficacy, capable of attenuating the individual and collective effects of the epidemic, but that viral variants have appeared whose antigens are slightly modified, new questions have been added to the previous ones. :
- will the immunity provided by the vaccines, which targets the sole S protein of SARS-CoV-2, be maintained at an effective level long enough to avoid systematic revaccinations?
- what factors influence the duration of protection?
- for whom is a booster injection necessary?
- will it have the expected effect on immunity? On protection against variants?
- are certain vaccines or combinations of vaccines better able to provide lasting protection?
- will the booster be more effective if it is done with the original vaccine or with a different vaccine?
- should the booster vaccine keep its original formulation or be adapted to the variant (s)? And which variant (s)?
- when should it be administered as part of the 2nd dose?
- if two doses of vaccine have not been sufficient to produce protective immunization in some people, will a 3rd dose succeed?
- even if the availability of vaccines no longer seems to be a problem in our countries, should we favor extending vaccination coverage (two doses for all, or one dose after an infection) or reserve a 3rd dose (and the necessary logistics) for part of the population?
- if the 3rd dose is not recommended for everyone, what are the criteria for identifying the people who should benefit from it?
- Will the recommendation of a 3rd dose call into question the health pass previously issued to the people concerned?
The answers to all these questions are still very incomplete. However, Israel and Germany have announced that they will offer a booster of the anti-covid vaccine to at least a part of their population considered at risk: people over 60 years old, who have not received an RNA vaccine, vaccinated among the first, vulnerable. The UK is reportedly preparing to revaccinate its entire population over 50 or immunocompromised. The United Arab Emirates and Turkey, which use Chinese-produced vaccines whose efficacy has been shown to be reduced in some studies, have started giving a 3rd dose to elderly subjects or medical personnel.
In France, the President has just confirmed his intention to administer a 3rd dose of vaccine which he believes would be necessary “not for everyone, immediately, but in any case for the most fragile and the oldest”, following in that other European countries. A reflection is launched for an implementation announced for the month of September.
Almost everywhere, and not only in France, the measures initially taken to control the covid 19 epidemic were adaptation measures, imposed by the situation. The virus has always stayed one step ahead. The decision to strengthen immunity with an additional dose of vaccine is of a different nature: it seeks to anticipate the possible failure of vaccine coverage in certain categories of the population and the emergence of SARS-CoV variants. 2 completely evading the immunity produced in response to the original virus or to vaccines derived from it. However, this choice, supported in France by the President of the Vaccine Strategy Orientation Council, ignores many unknowns and is akin to a bet made by countries that have the means and want to take the necessary steps for once. ahead in the epidemic. It is criticized by the WHO, which highlights the lack of data justifying this strategy but also the need to reserve vaccines for countries which have not yet been able to administer the first doses to their populations.
In a press release of July 16, setting out the main lines of its notice of July 15, 2021, the HAS indicated that from its point of view, “it is not necessary for the moment to propose a booster dose in the general population, and that it is necessary to follow the effectiveness of the vaccines in time including on any new variants that may appear “. She recommends the continuation of observations “in real life”, because “if it seems very likely that a booster injection will indeed provide a boost effect (whether with the same vaccine, a vaccine using another platform, or even a vaccine adapted to the variants of concern), the data available to date do not allow a precise evaluation of the impact or the need for such a booster on the prevention of vaccine failures. on this point”. A new notice is announced for the end of August.
The MesVaccins site will also continue its monitoring and public information work on this important subject.
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