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Vaccine efficacy is the percentage reduction of disease in a vaccinated group of people compared to an unvaccinated group, using the most favorable conditions. Vaccine efficacy was designed and calculated by Greenwood and Yule in 1915 for the cholera and typhoid vaccines. It is best measured using a double- blind, randomized, clinical controlled trials, such that they are studied under “best case scenarios.” 〔(Weinburg, G., & Szilagyi, P. (2010). Vaccine Epidemiology: Efficacy, Effectiveness, and the Translational Research Roadmap. Journal of Infectious Diseases, 201(11), 1607-1610.)〕 Vaccine effectiveness differs from vaccine efficacy in that vaccine effectiveness shows how well a vaccine works when they are always used and in a bigger population whereas vaccine efficacy shows how well a vaccine works in certain, often controlled, conditions. Vaccine efficacy studies are used to measure several possible outcomes such as disease attack rates, hospitalizations, medical visits, and costs. ==Vaccine Efficacy Formula== The outcome data (vaccine efficacy) generally are expressed as a proportionate reduction in disease attack rate (AR) between the unvaccinated (ARU) and vaccinated (ARV) studies can be calculated from the relative risk (RR) of disease among the vaccinated group with use of the following formulas. The basic formula〔(Orenstein WA, Bernier RH, Dondero TJ, Hinman AR, Marks JS, Bart KJ, et al. Field evaluation of vaccine efficacy. ''Bull World Health Organ'' 1985;63(6):1055-68 PMID 3879673. )〕 is written as: * VE = (ARU - ARV)/ARU (x 100). * VE= Vaccine efficacy * ARU= Attack rate of unvaccinated people. * ARV=Attack rate of vaccinated people 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Vaccine efficacy」の詳細全文を読む スポンサード リンク
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