Kwon KM, et al. Clin Exp Vaccine Res. 2017 Jul;6(2):156-159. https://doi.org/10.7774/cevr.2017.6.2.156

Choi WY, et al. Clin Exp Vaccine Res. 2015 Jan;4(1):11-16. http://dx.doi.org/10.7774/cevr.2015.4.1.11

Combination vaccines provide the versatile benefits of addressing different pathogens simultaneously using a combined formulation. This approach can be regarded as a substantial modernization in immunization. In this review, we highlight various advancements in combination vaccines based on mRNA, viral vectors, live attenuated, and recombinant vaccines. Recent success in clinical trials of mRNA platforms for combination vaccines has particularly accelerated research in this direction. The advantages of combination vaccines in terms of patient adherence, cost effectiveness, and streamlined immunization schedule are discussed. The existing challenges of antigenic interference, logistical hurdles, and the complications of regulatory standards are analyzed. Research trends to make combination vaccines viable for emerging infections have been summarized. The current work provides a critical overview, the existing opportunities, and the future prospects of combination vaccines.

Modernization of existing methods for the delivery of mRNA is vital in advanced therapeutics. Traditionally, mRNA has faced obstacles of poor stability due to enzymatic degradation. This work examines cutting-edge formulation and emerging techniques for safer delivery of mRNA vaccines. Inspired by the success of lipid nanoparticles (LNP) in delivering mRNA vaccines for COVID-19, a variety of other formulations have been developed to deliver mRNA vaccines for diverse infections. The meritorious features of nanoparticle-based mRNA delivery strategies, including LNP, polymeric, dendrimers, polysaccharide-based, peptide-derived, carbon and metal-based, DNA nanostructures, hybrid, and extracellular vesicles, have been examined. The impact of these delivery platforms on mRNA vaccine delivery efficacy, protection from enzymatic degradation, cellular uptake, controlled release, and immunogenicity has been discussed in detail. Even with significant developments, there are certain limitations to overcome, including toxicity concerns, limited information about immune pathways, the need to maintain a cold chain, and the necessity of optimizing administration methods. Continuous innovation is essential for improving delivery systems for mRNA vaccines. Future research directions have been proposed to address the existing challenges in mRNA delivery and to expand their potential prophylactic and therapeutic application.

Vaccination is one of the most successful strategies to prevent diseases caused by pathogens. Although various expression systems including Escherichia coli, yeast, insect, and mammalian cells are currently used for producing many of vaccines, these conventional platforms have the limitation of post-translational modification, high cost, and expensive scalability. In this respect, the plant-based expression system has been considered as an attractive platform to produce recombinant vaccines due to fast, cost-effective and scalable production as well as safety. This review discusses the development of plant-derived vaccines and the current stage of plant-based expression system.

Hong KJ, et al. Clin Exp Vaccine Res. 2018 Jul;7(2):145-148. https://doi.org/10.7774/cevr.2018.7.2.145