The clinical efficacy of influenza vaccination.

Inactivated influenza vaccine was developed approximately 50 years ago. The formulation has been continually improved, and its efficacy in preventing morbidity in healthy adults repeatedly demonstrated. Whether or not the vaccine is able to prevent hospitalisation and other complications of influenza in older individuals has been resolved by recent observational studies. During period of influenza virus circulation, the vaccine has also been shown to be effective in preventing hospitalisation and, in some cases, death from all causes and specific causes such as all respiratory conditions. Antivirals are also available for use against type A influenza, and may be especially valuable when antigenic change in the virus occurs. Now that questions regarding clinical effectiveness have been answered, vaccine and antivirals should certainly be more extensively used then in the past. The determinations of positive clinical effectiveness, which are based on observations of actual use of the vaccine, can form a basis for calculation of cost effectiveness.