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Figure 2: Relationship between percentage of cases vaccinated and vaccine efficacy Note: With this figure, vaccine efficacy could be assessed by the following formula: PCV = [PPV (PPV*VE)]/[1(PPV*VE)]. Here, PCV = Proportion of cases occurring among vaccinated individuals, PPV = Proportion of population vaccinated, and VE = Vaccine efficacy. If any of the two values in this formula is known, the third value can be derived 
