News on the dengue front, this sometimes very serious disease transmitted by the tiger mosquito. While the number of indigenous cases (i.e. people infected on mainland France) reached a new record this year, above 80, a new vaccine is now recommended in certain regions of the country. .
The High Authority for Health (HAS) recommends, this Tuesday, immunizing two population groups with the Qdenga vaccine from the Takeda laboratory: children and adolescents aged at least 6 years old who have already had dengue and adults aged 17 to 60 years old with risk factors (obesity, diabetes, sickle cell disease or other chronic illness, etc.). And this, in the overseas territories which are the most exposed (Antilles, Guyana, Reunion and Mayotte… ravaged by Cyclone Chido). Since the summer of 2023, around twenty deaths “directly attributable to dengue” have been recorded in Martinique and Guadeloupe, according to Public Health France.
Serological test offered to children
There is already a vaccine against dengue fever, Dengvaxia from the French group Sanofi. This was recommended in the Antilles in 2019, but only for residents who can prove that they have already had the disease. Indeed, the HAS had pointed out at the time a “risk of increase in serious cases in subjects who had not been infected before vaccination”.
This well-known phenomenon is called “antibody facilitation of infection” (ADE). It occurs when antibodies bind to a virus and then to a cell’s receptor… allowing the pathogen to infect the cell. Furthermore, the effectiveness of Dengvaxia was very uneven depending on the strain of the virus (there are four for dengue).
The data are more reassuring for the Qdenga vaccine, which obtained European marketing authorization in December 2022. “It is more attenuated than the Sanofi vaccine, and above all there does not seem to be any facilitation in naive people” , Stéphane Paul, member of the HAS Technical Commission on Vaccinations (CTV) told us in April. It also appears effective against all four serotypes.
As a precaution, only children who have already been infected will nevertheless be encouraged to be vaccinated. If in doubt, “a serological test may be offered to them,” indicates Anne-Claude Crémieux, president of the CTV. Young people with sickle cell anemia and who have never had dengue fever will still be able to be immunized, “on a case by case” basis and on medical advice.
Limit the circulation of the virus
Adults with comorbidities will be eligible, whether they have already caught the virus or not. “We asked ourselves the question of whether we should limit ourselves to those who have already been infected, but we risked missing out on a very vulnerable population. The severity of dengue is linked to the decompensation of comorbidities,” explains the scientist. People aged 60 and over remain outside the target, as there is no effectiveness data in this age group.
This campaign aims to limit the number of patients overseas. We do not know how effective the vaccine will be against transmission, and therefore on the arrival of infected people in mainland France. The tiger mosquito is now established in at least one municipality in each region of mainland France, and almost everywhere on the Mediterranean coast. By “biting” an infected person, it can then infect others. “Vector control measures, such as mosquito nets and emptying cups of stagnant water, remain essential,” insists Anne-Claude Crémieux.
It is now up to the Ministry of Health to take up this recommendation. Other vaccines could arrive in the coming years, such as that of the Butantan Institute in Brazil or that of a start-up hosted at the Pasteur Institute, V4C (“Vaccine for Communities”). And Anne-Claude Crémieux concludes: “We are still waiting for the ideal vaccine, but not in the immediate future. »
