Abstract: Adult immunization is a key component of life-course immunization, effectively reducing the burden of vaccine-preventable diseases and promoting public health and socioeconomic development. Focusing on the differences in adult immunization practices among different countries, this article conducts a literature review and policy analysis to systematically examine the immunization systems and adult vaccination strategies of representative countries or regions such as the United States, the United Kingdom, and Germany, comparing their approaches in terms of vaccination policies, service delivery mechanisms, and implementation pathways. The findings show that the public health value of adult vaccines has been widely recognized in many countries, with diverse practices and measures in place. In contrast, China still faces multiple challenges in advancing adult immunization programs, including low vaccination coverage, underdeveloped service systems, high out-of-pocket costs, and limited public awareness. Drawing on international experience, China can strengthen policy support and public education to increase adult vaccination rates, promote the integration of adult vaccines into the national immunization program, and strengthen the construction of the adult vaccination service system in China.