Journal of Vaccine Research 2024, Vol.14, No.6, 316-323 http://medscipublisher.com/index.php/jvr 318 3 Current Applications of mRNA Vaccines 3.1 Successful development and global deployment of COVID-19 vaccines The COVID-19 pandemic has significantly facilitated the creation and sale of mRNA vaccines. By marshaling global resources with remarkable speed and with unprecedented international cooperation, Pfizer-BioNTech's and Moderna's mRNA vaccine has achieved colossal success. The vaccines have been shown to be very effective at preventing COVID-19 infections and have received the nod of approval from regulatory authorities such as the U.S. Food and Drug Administration (FDA) (Chavda et al., 2022). The efficacy of these vaccines not only localized the outbreak, but also illustrated the potential of mRNA technology to rapidly develop vaccines against novel infectious diseases. 3.2 Progress in mRNA vaccines targeting other infectious diseases In addition to COVID-19, mRNA vaccine technology is being used to investigate prevention of other infectious diseases. With the potential for mRNA vaccines to quickly be redesigned to target a range of different pathogens, they have special utility against fast-evolving viruses. Existing research includes production of mRNA vaccines for influenza, Zika virus, and rabies. These vaccines induce a robust antigen-specific immune response by the expression of target antigens in cells, thereby triggering humoral and cellular immunity (Son and Lee, 2022). The flexibility and rapid development capabilities of the mRNA vaccines offer robust solutions to combat future infectious disease pandemics (Sun et al., 2023). 3.3 Current research and potential of cancer vaccines mRNA technology has also been applied to cancer immunotherapy. As a novel approach, mRNA cancer vaccine has high specificity and high efficacy, with less side effects than traditional treatments. These vaccines are expressed in antigen presenting cells (APCs) by encoding tumor-specific antigens, thereby stimulating the immune response to cancer cells (Xiao et al., 2022). At present, a variety of mRNA cancer vaccines are in preclinical and clinical trial stages, showing good prospects in the treatment of multiple solid tumors (Gote et al., 2023). Although challenges such as tumor heterogeneity and immunosuppressive tumor microenvironment still exist, the stability and effectiveness of these vaccines are constantly improving with the improvement of mRNA structural modification and delivery systems. 4 Safety and Efficacy of mRNA Vaccines 4.1 Durability of immune response and protective efficacy mRNA vaccines have elicited a robust and long-lasting immune response in clinical and preclinical trials. For instance, the mRNA-1273 vaccine, which codes for the prefusion-stabilized SARS-CoV-2 spike protein, induced strong binding and neutralizing antibody responses that were sustained through day 57 after vaccination. Additionally, mRNA vaccines have been capable of inducing cellular and humoral immunity, crucial for long-term protection against infectious diseases (Chu et al., 2021). The immune response to mRNA vaccines is not haplotype-restricted by MHC, making it possible for a more universal use across populations. 4.2 Common adverse reactions and side effect analysis after vaccination The general safety profile of mRNA vaccines is generally good, with most adverse events being mild to moderate in severity. Side effects are typically local (injection site pain, headache, tiredness), and tend to be transient, resolving spontaneously (Notarte et al., 2021). Severe adverse reactions are rare; for example, in phase 2 clinical trials of mRNA-1273 vaccine, one severe adverse event only was noted and this was rated as not vaccine-related. However, a few studies did show potential threats such as allergy, renal impairment, heart failure, and cytokine storms but these are not so common and tend to correlate with underlying pathology. 4.3 Safety studies in special populations Research on the safety of mRNA vaccines is a key area for the elderly, those with immunocompromised people and people with chronic inflammatory diseases. Studies have shown that although these special populations exhibit lower humoral immune responses compared with healthy individuals, the vaccine can still produce sufficient protective antibody levels and no significant adverse reactions were observed (Geisen et al., 2021). For example, immunosuppressed patients with chronic inflammatory diseases produce antibodies after vaccination
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