The use of a mixture model for estimating vaccine efficacy

In this note a mixture model is applied to examine the effects of vaccination. It can directly estimate the efficacy parameters and their standard errors for the two models suggested in Smith et al. (1994) and Haber et al.(1991a). Furthermore, it can be shown that the action of the vaccine for the two models are equivalent. We illustrate the procedure to an outbreak of mumps in a middle school in Ashtabula County, Ohio.