Use of influenza vaccine in non-high risk populations.

The aim of most strategies for vaccination against influenza is the prevention of mortality. Since individuals in the high risk group are mainly elderly, and the elderly have a low frequency of influenza infection, this strategy can have no significant controlling effect on morbidity. It has been shown in the longitudinal community study in Tecumseh, Michigan that highest frequency of infection with influenza is seen in the school-age population; this pattern is quite marked for type B influenza and less so for type A. In addition, it was possible in 1968-69 to show that vaccination of schoolchildren with an inactivated H3N2 vaccine resulted in a three-fold reduction in the attack rate for the entire community. Because of a number of problems in use of inactive vaccines, including the need for parenteral administration, it is unlikely that such preparations could be used regularly on this large a scale. However, it would be entirely feasible for live virus vaccines to be employed in such a manner. The use of more extensive vaccination would have an additional beneficial effect, since it has recently been shown in Tecumseh that a relationship may well exist between frequent respiratory infections and the development of chronic bronchitis in apparently healthy individuals.