Variational iteration and successive approximation methods for a SIR epidemic model with constant vaccination strategy

摘要

We consider a SIR epidemic model with constant vaccination strategy. An existing variational iteration method for solving the model is recalled. We provide a successive approximation method for this model. We prove that the existing variational iteration method is identical with the successive approximation method. Unfortunately, the existing variational iteration method (that is, the successive approximation method) is not accurate for large domains. Therefore, we propose an improvement to the existing variational iteration method and show that the improved variational iteration method is much more accurate than the existing one.