Microneedle Arrays for Painless Vaccine Delivery: A Critical Review of Design, Immunological Mechanisms, And Clinical Progress

Abstract

Conventional hypodermic needle vaccination suffers from barriers of needle phobia, sharps-waste generation, coldchain dependence and reliance on trained personnel that together undermine global immunization equity. Microneedle arrays (MNAs) are a revolutionary intradermal delivery platform that offers painless, minimally invasive antigen deposition in the antigen-presenting-cell-rich epidermis and dermis. This review covers four canonical MNA architectures (solid, coated, dissolving, and hollow) and hydrogel-forming and hybrid designs, and discusses the fabrication materials, release mechanisms, and immunological rationale. Peer-reviewed pre-clinical and clinical studies on influenza, COVID-19, HPV, dengue, rabies and Ebola vaccines are critically assessed. Clinical data show seroprotective immune responses with MNA-based intradermal vaccination comparable or superior to IM injection at antigen doses reduced by up to 80%. Key translational barriers such as antigen stability, dose-volume limitations, regulatory complexity and aseptic manufacturing are reviewed alongside emerging solutions such as 3D-printed geometries, delivery in conjunction with iontophoresis and stimulus-responsive polymers. MNAs are a scientifically mature platform, requiring accelerated clinical validation and regulatory harmonization to make a transformative impact on global public health.