Influence of Microbiota on Vaccine Effectiveness: "Is the Microbiota the Key to Vaccine-induced Responses?"

Vaccines are one of the most powerful tools for preventing infectious diseases. To effectively fight pathogens, vaccines should induce potent and long-lasting immune responses that are specific to the pathogens. However, not all vaccines can induce effective immune responses, and the responses vary greatly among individuals and populations. Although several factors, such as age, host genetics, nutritional status, and region, affect the effectiveness of vaccines, increasing data have suggested that the gut microbiota is critically associated with vaccine-induced immune responses. In this review, I discuss how gut microbiota affects vaccine effectiveness based on the clinical and preclinical data, and summarize possible underlying mechanisms related to the adjuvant effects of microbiota. A better understanding of the link between vaccine-induced immune responses and the gut microbiota using high-throughput technology and sophisticated system vaccinology approaches could provide crucial insights for designing effective personalized preventive and therapeutic vaccination strategies.