Influenza causes considerable morbidity and mortality and the damage to public health can be considerable. The most effective measures available for the prevention of influenza is vaccination. In most industrialised countries the objective of vaccination is to limit the disease among individuals at risk, especially the elderly. During the winter of 2000/2001, General Practitioners (GPs) monitored 14,818 elderly individuals. The objective was to evaluate the weekly incidence of the disease. Furthermore, we carried out a prospective study on 512 elderly individuals, arranged according to vaccination (304 vaccinated and 208 non-vaccinated), with the main objective of assessing the costs of the disease and the efficacy of vaccination. Finally, in order to assess the percentage of vaccinated elderly individuals, we carried out a telephone survey on 500 subjects. Our clinical surveillance study enabled us to establish that morbidity was particularly low in elderly individuals.The results of the prospective study allowed us to estimate the cost-benefit ratio at 8.22, with a net saving of 110.20 Euros for each vaccinated subject. We were also able to establish that the vaccine coverage among elderly individuals was 63%. Our study, though carried out during a low epidemic year, confirms the economic advantage of vaccination in the elderly.