The COVID-19 pandemic highlighted the urgent need for effective vaccine policies, but traditional clinical trials often lack sufficient data to capture the diverse population characteristics necessary for comprehensive public health strategies. Ethical concerns around randomized trials during a pandemic further complicate policy development for public health. Reinforcement Learning (RL) offers a promising alternative for vaccine policy development. However, direct online RL exploration in real-world scenarios can result in suboptimal and potentially harmful decisions. This study proposes a novel framework combining tabular Q-learning with microsimulation, where a Recurrent Neural Network (RNN) serves as a digital twin environment simulator of the target population. This digital twin captures temporal associations between infection and patient characteristics to generate realistic individual disease trajectories, enabling safe and efficient policy learning without real-world interaction. Our tabular Q-learning model produces an interpretable policy table that balances the risks of severe infection against vaccination side effects. Applied to COVID-19 booster policies, the learned Q-learning-based policy outperforms current practices, offering a path toward more effective vaccination strategies. A project webpage introducing our work, including links to the software, a brief introductory video, and a step-by-step tutorial video, is available at https: //public. websites. umich. edu/j̃iankang/software/dtplwebsiteᵤmich/index. html.
Ma et al. (Mon,) studied this question.