RESUMO
<p><b>OBJECTIVE</b>To estimate the effectiveness of inactivated influenza vaccine in elderly population.</p><p><b>METHODS</b>An quasi-experimental study was used. 590 elderly people who volunteered to receive the influenza vaccine were served as vaccine group, while 602 persons who did not want to receive the inoculation but could match the vaccine group were served as controls. One baseline and three follow-up surveys were carried out.</p><p><b>RESULTS</b>The protective rates of influenza like ill (ILI) as 52.38%, 36.84% and 37.89% with the decreasing rates of visits to ILI clinic as 45.16%, 50.54% and 50.54% were found after 1 month, 3 month and 6 month of inoculation of influenza vaccine; The protective rates of common cold, other respiratory tract or chronic disease were 49.54%, 64.54%, and 38.82%, respectively. The benefit-cost ratio was 4.98:1 in elderly population.</p><p><b>CONCLUSION</b>Influenza vaccination could decrease ILI incidence and recurrence rates of related chronic diseases on elderly population to provide better economic benefits for the elderly.</p>