Figure 2. Markov cycle tree.

The cycle tree gives more detail on the programming of the Markov model. Health states are the first branches off the Markov node. Pneumococcal diseases (invasive pneumococcal disease, IPD and nonbacteremic pneumococcal pneumonia, NPP) are modeled as virtual states (“tolls”) within the tree structure. The triangular terminal nodes (on the left) depict the health states where portions of the cohort following that path will begin the next yearly cycle of the model.