Vaccin antigrippal en situation d'émergence

Avian Influenza viruses emergences are more frequent than pandemic events. Since 1976 several cases of human infections with avian or swine Influenza, such as H1, H3, H5, H6, H7, H9, and H10, have been reported. However only H1N1pdm09 caused a pandemic. The enhance surveillance at international level provides a rapid detection of these zoonotic infections. For each iterative emergence, one should ask if it is necessary to produce a new vaccine. The identification of a vaccine candidate and the production of the corresponding vaccine seed is a careful approach in order to get ready to produce the vaccine in the context of a pandemic. Indeed, identification of a vaccine candidate and the production of the corresponding vaccine seed have already been done for several emergent viruses. However, stockpiling and use of vaccine was only done for H5N1. The H5N1 and H1N1pdm09 experiences highlighted that vaccine production must undergo several necessary steps before use. Vaccine composition and immunization schedules are dependent of virus history and pre-existing immunity of the exposed population. Indeed immunization schedules appear to differ according to the viruses. The evaluation of post-vaccine humoral immunization response suggest that immunization against Influenza sub-types that previously circulated in human population may only require one injection whereas a new sub-type may need two injections with an adjuvant. Actually, new dosage formulation based on live attenuated vaccines, virosomes, or pseudo-particles are up-coming and may provide alternative to a conventional arsenal. Vaccine production is the major part of the public health answers to Influenza emergence. Vaccine use, during national vaccination campaign, requires a good compliance from both healthworker and population. Success or failure depends on the population perceived risk and its compliance to the selected vaccine strategy.