Pushing the second injection back in the under-55 age bracket would "accelerate the vaccination campaign...and achieve herd immunity much faster with the same number of doses, while ensuring satisfactory individual protection", the National Academy of Medicine said in a statement on Thursday.
The academy has no decision-making power in France, unlike the High Authority for Health (HAS), which can make such recommendations with the backing of the government.
On Wednesday, the delay between the first two doses of the Pfizer/BioNTech and Moderna vaccines, which use new messenger RNA technology, was extended from 4 to six weeks.
"This will allow us to speed up the vaccination campaign without compromising public protection," Health Minister Olivier Véran explained to French weekly Journal du Dimanche.
High-risk professions
The Academy of Medicine said that, based on recent studies in the United States and United Kingdom, a single dose of the mRNA vaccine had been shown to provide very high level of protection against the coronavirus.
With the more contagious British variant now the dominant strain in France, the academy said it made sense to delay second injections for those aged under 55 years with no history of immune deficiency, to allow more people in high-risk professions, such as teachers, to receive their first dose.
In France, the only under-55s currently eligible for the vaccination are frontline priority workers (health workers, home care workers, firefighters) or those with pre-existing health conditions.
Some scientists are reluctant to extend the delay between doses, fearing incomplete protection provided by the first injection may favour the emergence of new variants.
The academy also called for the first injection to be postponed in the case of patients who had tested positive for the coronavirus within the preceding six months.
