Mapping the Evolution of Vaccine–Microbiome Research: A 30-Year Bibliometric Analysis (1995–2025)

Background: Vaccine efficacy shows marked inter-individual heterogeneity, and the gut microbiome critically shapes vaccine-induced immune responses. However, the field’s developmental trajectory remains uncharacterized. Methods: Publications on vaccines and microbiome (1995–2025) were retrieved from the Web of Science Core Collection. After screening, 4945 documents (3620 articles, 1325 reviews) were analyzed using CiteSpace, VOSviewer, and Bibliometrix for collaboration networks, co-citation, keyword clustering, and burst detection. Results: Annual output increased from 21 (1995) to 496 (2025), with citations reaching 27,181 in 2025, indicating accelerated post-2016 growth. The USA dominated (1431, 28.94%), followed by England (501) and China (483), though China’s betweenness centrality (0.01) revealed limited collaborative influence. Among the 25 references with detected citation bursts, 10 remained active in 2025, five of which concerned COVID-19. Keyword evolution showed a paradigm shift from single pathogens to ecosystem interactions (“gut microbiota,” “immune response”). Conclusions: The field is expanding rapidly, accelerated by the COVID-19 pandemic. US–European dominance persists; China shows rapid growth but limited international collaboration. Research has shifted to trained immunity, the gut–lung axis, and metabolite regulation. Multi-omics and AI integration will drive precision vaccinology.