The flu shot by the skin is more effective

► How does the current flu shot work?

This winter, more than 2,000 deaths are attributable to influenza, according to data from Public Health France. If the flu still kills every year, a flu vaccine exists to protect the populations. This is the best way to prevent the disease and reduce the risk of serious complications or death.

Nevertheless, its effectiveness does not reach 100%. This is due to the fact that its composition is set each year by the WHO (World Health Organization) several months before the outbreak of epidemic peak and so it is based only on the probability that this or that strain of influenza sequestered during the coming winter.

Why do we catch flu in winter?

" Influenza viruses are indeed very changing and the composition of the vaccine must differ from one year to anotherexplains Combadière Behazine, Center for Immunology and Infectious Diseases (Inserm-Sorbonne University). However, since it takes 5 to 6 months to develop, the vaccine does not always target all circulating strains. "

► What does the injection mode change?

The team of Behazine Combadière has been working for years on the impact of vaccine delivery routes on the quality of immune responses. Indeed, vaccines are usually administered by "muscular way", usually in the deltoid muscle in the upper arm, have two effects: the first is to produce antibodies, these circulating proteins in the blood, secreted by white blood cells, and which encircle the virus to destroy it (called humoral response). The second is to stimulate the production of other white blood cells, called "killers", which directly destroy the infected cells (called the cytotoxic response).

In view of the insufficient effectiveness of current vaccines, the team looked into the value of "cutaneous routes" by intradermal injection (in the dermis) or by transcutaneous application (hair follicle route). For that a clinical trial phase I (the product is it safe?) And phase II (the product has a beneficial effect?) Was conducted on 60 people aged 18 to 45, in collaboration with the Cochin-Pasteur Clinical Investigation Center for Vaccinology.

The published study demonstrates that the skin routes induce in some subjects a cytotoxic response after influenza vaccination (1). "This result argues in favor of considering this route of injection of the vaccine, insofar as it triggers an additional immune response to that obtained in the context of a conventional vaccination. These cytotoxic responses would be particularly protective in the elderly after influenza vaccination ", explains Combadière Behazine.

► What else does this essay bring?

Beyond these results, the team brought new elements concerning the specific imprints left by these injection routes in the body. The researchers spotted a dozen proteins of innate immunity appeared one day after the injection of the vaccine.

Towards a universal flu shot

The idea now is to identify, among this ten or so biomarkers, who can predict whether the immune response is good, and therefore whether the vaccine is effective. If the response is insufficient, the doctor can then give a second injection or increase the dose. "These latest results, however, still require further studies to validate the interest of these biomarkers and their subsequent use", concludes Behazine Combadiere.