The Gut Microbiome and Vaccination: A Comprehensive Review of Current Evidence and Future Perspectives.

The gut microbiome has emerged as a pivotal player in shaping host immune responses, with significant implications for vaccine efficacy and safety. Rather than detailing all influencing factors, this review focuses on the most critical and translational aspects of microbiome-vaccine interactions. Increasing evidence shows that the composition and functionality of the intestinal microbiota can influence both the magnitude and durability of vaccine-induced immunity. For instance, Bifidobacterium longum supplementation was shown to enhance influenza vaccine seroconversion rates by approximately 30% in clinical and preclinical models, underscoring the translational potential of microbiome modulation. Here, we provide a concise synthesis of mechanistic insights and key clinical findings that connect gut microbial composition and metabolism with vaccine outcomes. We further highlight microbiome-targeted interventions-such as probiotics, prebiotics, and postbiotics-that hold promise for optimizing vaccine responses in diverse populations. By emphasizing actionable evidence over descriptive variability, the review aims to clarify how microbiome modulation can be strategically harnessed to improve vaccine performance. Integrating microbiome modulation into vaccination strategies may enhance global immunization equity and effectiveness, offering a feasible pathway toward more durable and inclusive protection worldwide.