For many years, the serious consequences of influenza were generally thought to be limited to older persons and those with underlying chronic conditions. Use of vaccine was directed to these groups. Gradually, however, therecommendationsfor influenza vaccination were expanded to include, first, young children and, subsequently, all those 18 years of age or younger.1,14-16 Persons who are in close contact with those at increased risk, whatever their age, are also included in the
current recommendations for vaccination, which thus apply to a major portion of the population.