In Reply We were interested to read the responses to our Research Letter regarding substandard vaccine compliance and the 2015 Disneyland measles outbreak. The authors raise several questions regarding our modeling method and resulting vaccination rate estimates.
As cited by Blumberg et al,1 the incidence decay and exponential adjustment (IDEA) model does not consider transmission heterogeneity; in this way, it is a simplification of reality, as all models are. We agree that this is an important consideration and we were pleased to see that Blumberg et al1 incorporated heterogeneity in their own analysis of the Disneyland measles outbreak. However, we believe that the results obtained from the IDEA model are valuable in that they effectively highlight the pervasiveness of vaccine hesitancy clusters in the United States, a phenomenon that directly contributes to increased risk of disease transmission.