Objectives: Influenza disease considered to be more sever and complicated in old age persons, because immune response diminish in this group. This disease is one of the main causes of mortality in elder people. The prevalence of influenza disease in elderly are living in nursing home is more in compare if they dwell in community. We studied the effect of influenza vaccine on the incidence and numbers of episodes of influenza like illness (ILI) and cost of cares in old population residing in Kahrizak Charity Foundation, during nine months period from December of 2004 Through September 2005.

Methods & Materials: This Cohort study was executed in the Kahrizak Charity Foundation, which is located in southwest of Tehran. Outcomes of residents whom were administrated influenza vaccine (n=389) and control subjects whom weren't administrated influenza vaccine (n=557), monitored clinically for onset of ILI and its relative drugs, radiology and laboratory costs. Range of participant's ages were 60-105 years.

Results: For intervention group one dose of inactivated, subunit trivalent influenza vaccine was administered. During December 2004 to September 2005, 10.9% of participants caught ILL There were statistically significant lower percents of ILI (7.2% in vaccinated group and 13.4% in unvaccinated control group). Lower of drugs, laboratory and total costs in vaccinated group in compare to unvaccinated group (Consequently 1174±4918, 48500±119362 and 90690±119962 in vaccinated group versus.2521±8710, 179494±408479 and 183015±43634 in unvaccinated control group. There wasn't significant difference in deaths between vaccinated group and unvaccinated control group (65 case in vaccinated group and 66 case in unvaccinated group and Odds ratio=1.04). No serious adverse reactions to vaccination were recorded. Thus, influenza vaccination is safe and effective in this population and should become a part of the routine care of old persons who are dwelling in nursing homes.

Conclusion: This study implicates clinical efficacy and cost- benefit of influenza vaccination in nursing home residents in Iran. Annual influenza vaccination of old people requires the attention of all nursing home attendants, physicians, and public health organizations.