BACKGROUND: There has been much debate about the appropriate statistical 
methodology for the evaluation of malaria field studies and the challenges in 
interpreting data arising from these trials.
METHODS: The present paper describes, for a pivotal phase III efficacy of the 
RTS, S/AS01 malaria vaccine, the methods of the statistical analysis and the 
rationale for their selection. The methods used to estimate efficacy of the 
primary course of vaccination, and of a booster dose, in preventing clinical 
episodes of uncomplicated and severe malaria, and to determine the duration of 
protection, are described. The interpretation of various measures of efficacy in 
terms of the potential public health impact of the vaccine is discussed.
CONCLUSIONS: The methodology selected to analyse the clinical trial must be 
scientifically sound, acceptable to regulatory authorities and meaningful to 
those responsible for malaria control and public health policy.