evidence: Nucleic acid-based vaccines have shown remarkable potential, as manifested by recent FDA approval for emergency use of two mRNA vaccines (BNT162b2 by Pfizer/BioNTech and mRNA-1273 by Moderna) for combating the COVID-19 pandemic. Their impressive efficacy can be largely attributed to the successful LNP delivery platforms, which are used extensively for the delivery of other mRNA vaccines176,177. For example, saRNA encoding the SARS-CoV-2 spike protein encapsulated in LNPs achieved high and dose-dependent SARS-CoV-2-specific antibody titres in mouse sera, leading to neutralization of pseudotyped and wild-type virus14. The potency of mRNA vaccines could be boosted by nanoparticle-mediated co-delivery of immunostimulatory adjuvants178. Recently, lipid adjuvant-assisted mRNA vaccines were developed by high-throughput screening of ionizable or cationic lipids, which can simultaneously mediate mRNA delivery and provide adjuvant stimulation via the STING pathway or Toll-like receptor 4 pathway179. Beyond LNPs, polymeric nanoparticles and some inorganic nanoparticles have also been adopted to deliver nucleic acids for vaccination (Fig. 6c).