Covid-19: the vaccine booster will be essential in the face of the “moderate epidemic recovery” according to Arnaud Fontanet – LCI

He had predicted it in September: “The epidemic should restart this fall”. While the incidence rate in France has just passed the alert threshold of 50 cases per 100,000 people again, the epidemiologist and member of the Scientific Council Arnaud Fontanet now qualifies the increase in contamination (around 5,000 cases per day currently) of “moderate epidemic recovery”.

A recovery due in part to the drop in temperatures and the fact that “we go back to living inside, windows closed”, according to the scientist. “With us in France, there is a variation of about 33% of the R0 between the coldest and the hottest periods”, he explains. The impact of temperature is however minor compared to “the arrival of a more transmissible variant”, like the Delta or its subvariants with variable transmissibility.

The doctor also pointed to the drop in the effectiveness of vaccines against contamination. “Even if the latter continue to protect more than 90% against severe forms of the disease, protection against infection increases from 80% two months after the second dose to 50% after six months”, he exposes. It is in 18-49 year olds, vaccinated in early summer and “often involved in outbreaks of epidemics” than “the decline in vaccine efficacy will be felt”, predicts Arnaud Fontanet. He nevertheless underlines a slight decrease in the effectiveness of the vaccine for severe forms, which can fall under 90% “among the oldest and most fragile”.

Despite the recovery, the epidemiologist is fairly confident in France’s ability to avoid hospital saturation. For this, according to him, only one solution: the booster dose, the campaigns of which have already been launched for several weeks among those over 65. “Everything must be done to complete the first-time vaccinations, especially in the most vulnerable and consolidate this experience by means of boosters”, supports Arnaud Fontanet.

“A booster dose increases the concentration of neutralizing antibodies to levels five to ten times higher than those obtained after a second dose, he exposes, divides the risk of infection by ten and the risk of hospitalization by twenty, compared to people who have received two doses but no booster injection “. A measure that could become necessary in all adults “if we do not manage to complete the primary vaccinations and booster doses in the most fragile”.

Two other viruses could also create tension in hospitals this winter: “That of the flu and the one responsible for bronchiolitis in children under 2 years “, the consequences of which could be exacerbated by the lack of immunity maintained in the population over the past two years.

On the vaccination of children from 5 to 11 years old, still under debate, the doctor is procrastinating. “We must carefully analyze the benefit-risk ratio in this age group where severe forms remain very rare”, he explains.

While the Haute Autorité de Santé (HAS) should soon present its recommendations on the subject, “This will make it possible to observe the risk of undesirable effects in this age group on millions of vaccinated children (…). The undesirable effects occurring no later than two months after the injection, we should be fixed in February”, he concludes.