Necessary precaution in order to strengthen the immunity against COVID-19 or a measure without scientific basis and unequal towards poor countries? The possibility of a third tranche vaccine for the whole population, is the subject of intense debate.
Some countries, such as France, have started to give this booster dose to certain categories of the population: the elderly (six months after vaccination) and immunocompromised people.
To justify this, these countries cite a decline in the effectiveness of vaccines against infection with Delta variant, a decline that seems to be accelerating as time goes by.
Other governments have gone further or want to go further. In Israel, the third dose is available from the age of 12 years, five months after vaccination. The United States plans to launch a booster campaign for all Americans with the Pfizer and Moderna vaccines from 20 September.
A measure that the World Health Organization (WHO) has repeatedly condemned.
«At this time, we do not wish to see a generalized use of booster doses for people in good health who have been fully vaccinated,» the agency's director general reiterated the other day, Wednesday, Tedros Andanom Gebreyes.
«I will not remain silent as long as the companies and countries that control the world's vaccine supply believe that the world's poor have to make do with the leftovers,» he said, exasperated.
What benefit?;
From a scientific point of view, there is a consensus around giving a third dose to people who are «immunocompromised», i.e. those whose immune system is weakened (by a cancer or an organ transplant, for example). Studies have shown that, despite vaccination, their bodies did not produce enough antibodies (the main criterion for assessing the effectiveness of vaccines).
Although with less data, the same reasoning applies to the elderly, whose immune system has become less effective due to ageing.
On the contrary, scientists question the usefulness of a booster dose for young people in good health, citing a lack of scientific evidence.
«We are not sure that the benefit will be greater,» cardiologist Florian Jorès of the French collective Du côté de la science, which is committed to defending the integrity of science, tells Agence France-Presse.
As he says, «we can do surveys, think about target populations instead of doing a third dose to the whole population, or quantify antibodies» to determine whether or not someone needs that booster dose. «It would be a little bit smarter from a scientific point of view,» Dr. Zoresh reckons.
«Boomerang»
After all, the issue of inequality in access to vaccines between rich and poor countries, raised by the WHO, is not only moral. It is also real at the health level.
«I am not at all sure that the priority of rich countries should be to provide a third dose before a large proportion of the world's inhabitants have received the first two,» epidemiologist Antoine Flao tells AFP.
Because, by allowing the virus to spread over a large part of the world, it could become a «particularly serious boomerang for rich countries if these exotic epidemics cause new, more contagious variants to escape existing vaccines,» he says.
According to Professor Flao, Director of the Institute of Global Health at the University of Geneva, the generalisation of the third dose in Israel will serve as a learning experience for the rest of the world.
«If the benefit of the third tranche is significant, experts will be more inclined to support the principle of granting it,» he predicts.
«If this benefit remains marginal, the question should be asked what is the best strategy at this time: to vaccinate with the third dose the populations of the richest countries of the world, offering them a marginal benefit and leaving the poor with a very weak protection, or, on the contrary, to vaccinate the whole planet first?» he concludes.
