Modeling is generally used to study complex systems. Furthermore, computer simulation of models is a popular way to examine and study analytically intractable models. While these practices are quite popular, it is important to use them judiciously. Models can be created that cannot be verified or validated. Furthermore, using simulation results without proper analysis can lead to false claims. Also, an emerging field of modeling, agent-based modeling, is a field that deserves special attention due to the complexity of the behaviors modeled. Agent-based models define rules for agents to follow and their interactions are then simulated to observe the effects of their resultant behavior. An agent-based model of epidemic spread through a population is presented which leads to some unintuitive results regarding the effects of immunization.