•Most studies prior to 2004 lack formal randomization
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•Not possible to mask participants or interviewers
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•Only two studies used techniques to control for clustering
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•Limited measurement on hygiene / soap use
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•Varying definitions of symptoms and reporting methods across studies
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•All studies were conducted outside of USA
–High risk populations
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•Difficult to tease apart the effect of soap use from that of hygiene education
–Only one study asked participants to follow regular routine
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