Global public health faces substantial challenges from malignant tumors and infectious diseases. Vaccination provides an approach for treating and preventing these diseases. Oral vaccinations are particularly advantageous in disease treatment and prevention due to their non-invasive nature, high patient compliance, convenience, cost-effectiveness, and capacity to stimulate comprehensive and adaptive immune responses. However, the overwhelming majority of oral vaccines remain in experimental development, struggling with clinical and commercial translation due to their suboptimal efficacy. Thus, enhancing scientists' understanding of the interaction between vaccines and gastrointestinal immune system, creating antigen delivery systems suitable for the gut mucosal environment, developing more potent antigenic epitopes, and using personalized combination therapies are critical for advancing the next generation of oral vaccines. This article explores the fundamental principles and applications of current oral anti-tumor and anti-infective vaccines and discusses considerations necessary for designing future oral vaccines.