Number-needed-to-vaccinate calculations: Fallacies associated with exclusion of transmission

Abstract

Highlights

* Number-needed-to-vaccinate calculations are common metrics of vaccine efficiency. * Traditional NNV calculations ignore indirect "herd" effects. * Exclusion of herd effects may result in extreme upward bias of NNV. * Bias is most problematic for diseases with lowR0and partially effective vaccines. * Traditional NNV calculations should be used sparingly and interpreted with caution.