[Basis for vaccine recommendations].

Once a new vaccine has been granted its licensing, a public health expertise is needed in order to support the decision regarding its possible inclusion within the national immunisation schedule. This analysis, based on an assessment of the benefits/risks balance and costs/effectiveness ratio, is a multidisciplinary exercise. Largely based on epidemiological and immunological expertises, it also requires bio-mathematical and economical inputs, if the long term consequences of the vaccination are to be taken into account. Indeed, the main drivers of the decision are the burden of the disease, the characteristics of the vaccine in term of effectiveness and safety, the cost of the vaccination, the feasibility of the adjunction of the vaccine in the schedule, the social demand for this vaccination and the positive or negative indirect effects of a large vaccination on the epidemiology of the disease, in addition to the direct protective effect for vaccinated individuals. New vaccines are generally characterised by a more limited epidemiological impact than older vaccines, in a context of growing requirements from our society regarding drugs, and especially vaccines, safety. Both the real and perceived benefits/risks balances for the more recent vaccines appear questionable. The possibility of detrimental epidemiological consequences of either insufficient vaccination coverage or serotype (or serogroup) replacement is another factor that makes the decision regarding vaccination strategies increasingly complex.