ESTIMATION OF VACCINE EFFICACY IN THE PRESENCE OF WANING - APPLICATION TO CHOLERA VACCINES

The authors present a nonparametric method for estimating vaccine effi cacy as a smooth function of time from vaccine trials. Use of the meth od requires a minimum of assumptions. Estimation is based on the smoot hed case hazard rate ratio comparing the vaccinated with the unvaccina ted, The estimation procedure allows investigators to assess time-vary ing changes in vaccine-induced protection, such as those produced by w aning and boosting, The authors use the method to reanalyze data from a vaccine trial of two cholera vaccines in rural Bangladesh. This anal ysis reveals the differential protection and waning effects for the va ccines as a function of biotype and age.