[Vaccinations: a necessity]

The preventive efficiency of vaccination for numerous infectious diseases remains up to date. Multiple epidemiological data are documenting the underuse of this approach. Risk situations are briefly reviewed, specially those related to unappropriated immunologic functions associated with ageing. Both extremes of life can display insufficient responses to vaccines, either by immaturity or immunosenescence. The diagnostic interest of these situations, by following the vaccinal responses, resides in allowing some prophylactic treatments (antibiotics, gammaglobulins) or consider immunostimulating treatments. This is not to speak, for the older subjects, about the repletion of multiple deficits of their nutritional status.