One of important goals of vaccine development is to identify potential immunological markers that predict vaccine efficacy. Having such a predictive marker can substantially accelerate the vaccine development as subsequent studies can be conducted efficiently based on these immunological markers instead of efficacy endpoints. In this talk, we will discuss statistical issues involved in assessing the predictive value of immunological markers. Statistical properties of some commonly used approaches including the Prentice’s criteria and a recently developed causal inference framework will be discussed. A real vaccine example will be used to illustrate the methods.