A distinction must be made between measures of vaccine efficacy for which the increased specificity of CXR-confirmed pneumonia plus CRP ≥120 mg/l plus procalcitonin ≥5 ng/ml over CXR-confirmed pneumonia alone is apparent, and studies of the burden of disease prevented (VAR), which are optimised when vaccine sensitivity is maximised. The gene discussed is CRP; the disease is susceptibility to pneumonia measurement.