From obstacles to opportunities: Innovations and evolution of strategies in scrub typhus vaccine research.

Scrub typhus, caused by the obligate intracellular bacterium Orientia tsutsugamushi, remains a major public health burden in the Asia-Pacific region and is increasingly reported beyond its traditional endemic range. Despite its clinical significance, progress toward vaccine has been limited, largely due to extensive antigenic diversity and the difficulty of inducing durable cross-protective immunity. This review attempts to retrace the historical path of scrub typhus vaccine development from whole-cell killed preparations to subunit proteins, recombinant constructs, and epitope-driven strategies. Recent advances in reverse vaccinology, structural modeling, and nanotechnology-based delivery systems including virus-like particles and mucosal nanoparticles offer rational strategies to enhance immunogenicity and broaden strain coverage. Together, these approaches reflect a transition from empirical vaccine design to rational, biology-informed strategies aimed at clinical translation. Success along this pathway will require increased orbiting of computational design, advanced delivery platforms, and clinical validation toward the fulfilment of effective solutions to endemic populations.