THE COMPARISON OF INFLUENZA VACCINE EFFICACY ON RESPIRATORY DISEASE AMONG IRANIAN PILGRIMS IN THE 2003 AND 2004 SEASONS

Prolonged cough occurs in a large proportion of the 2 million pilgrims who participate inthe annual hajj in saudi arabia. there is not any unique cause for pilgrims’ respiratory involvement,but several studies suggest a high incidence of influenza as a cause of the disease. to determineinfluenza vaccine efficacy against respiratory disease in pilgrims, we conducted two similar cohortstudies on 51100 iranian pilgrims who had participated in the annual hajj in the years 2003 and 2004.we calculated vaccine efficacy in these two years with the use of “1- odd’s ratio” formula andcompared the results. the vaccine efficacy for prevention of influenza like illness in the year 2003 was51% but the vaccine was not efficient in the year 2004. it was concluded that etiologic agents other thaninfluenza virus should be considered as the cause of respiratory disease in hajj. bacterial infectionssuperimposed on chronic respiratory diseases, and allergic or toxic conditions are suggested courses formore investigation.