We thank Dai et al for their interest in our article. It seems that that they have misunderstood several aspects of our article, and we are writing to clarify as many as we can in a brief letter. For example, they assert our reported time trends of Clostridium difficile infection (CDI) incidence may be inaccurate because of change in the method of testing. However, the method of testing changed in only the last year of the study and excluding that year in a sensitivity analysis had no effect on the study findings.