mRNA vaccines have emerged as promising alternatives to conventional vaccines because of their flexible design, high immunogenicity, favourable safety profile, efficacy and potential for rapid clinical development. The accelerated development of mRNA vaccines during the COVID-19 pandemic has revolutionised the field of vaccinology, highlighting their potential for combating emerging infectious diseases. The mRNA platforms can induce robust humoral as well as CD4+ and CD8+ T-cell-mediated immunity, offering broader protection than subunit protein vaccines. Consequently, they have been extensively studied against a wide range of viral, bacterial and parasitic infections, although the development of mRNA vaccines against bacterial and parasitic infections has lagged behind those targeting viruses. This review highlights recent studies on mRNA vaccine development and applications against a wide range of infectious diseases including non-COVID viral infections, bacterial pathogens such as Mycobacteria or Pseudomonas aeruginosa and parasitic infections, including malaria. Moreover, it discusses key optimisation strategies and highlights candidates that have progressed to clinical trials, and the current challenges in enhancing immunogenicity and improving delivery systems.