Klebsiella pneumoniae vaccines: Evolving the blueprint from traditional platforms to mucosal and nanoscale delivery

<i>Klebsiella pneumoniae</i> (<i>KP</i>) is a critical global health threat due to carbapenem-resistant and hypervirulent strains, necessitating effective vaccines amid declining antibiotic efficacy. This review provides a timely and systematic analysis of the current <i>KP</i> vaccine landscape. We first outline the epidemiology of classical and hypervirulent <i>KP</i> (<i>hvKP</i>) and the corresponding protective host immunity, establishing a foundation for vaccination. A detailed survey of key antigenic targets, including polysaccharides and proteins, is presented. The core of this review critically assesses the spectrum of vaccine platforms, from traditional whole-cell and subunit vaccines to nanovaccine platforms. Distinctively, we place a dedicated focus on two transformative frontiers: nanovaccines-such as outer membrane vesicles (OMVs) and biosynthetic glycoconjugate nanoparticles-and mucosal vaccination strategies, emphasizing their unparalleled potential to block infection at the primary site of colonization. By synthesizing cutting-edge preclinical advances and addressing persistent translational challenges, this review serves as a timely and comprehensive resource, offering valuable insights to guide the future development of effective immunization strategies against this formidable pathogen.