Journal of Vaccine Research 2024, Vol.14, No.3, 95-106 http://medscipublisher.com/index.php/jvr 100 responses and provide protection against various viral pathogens, underscoring the broad applicability of this technology (Zhang et al., 2019). 5.2 COVID-19 pandemic response The COVID-19 pandemic accelerated the development and deployment of mRNA vaccines, highlighting their potential in addressing global health crises. The rapid spread of SARS-CoV-2 and the urgent need for an effective vaccine led to the unprecedented speed at which mRNA vaccines were developed, tested, and authorized for emergency use. The Pfizer-BioNTech (BNT162b2) and Moderna (mRNA-1273) vaccines were the first mRNA vaccines to be widely used in humans, showcasing the ability of mRNA technology to respond quickly to emerging infectious diseases (Kim et al., 2021). Arunachalam et al. (2021) comprehensively analyzed the innate and adaptive immune responses of 56 healthy volunteers following vaccination with the Pfizer-BioNTech mRNA vaccine (BNT162b2) (Figure 3). The study found that post-vaccination, volunteers generated neutralizing antibodies against both the SARS-CoV-2 prototype virus and the B.1.351 variant, with a significant increase in antigen-specific multifunctional CD4 and CD8 T cells after the second dose. The research showed that the second vaccine dose induced a stronger innate immune response compared to the first dose, including an increased frequency of CD14+CD16+ inflammatory monocytes, elevated plasma IFNγ concentrations, and transcriptional signatures of antiviral innate immunity. Additionally, single-cell transcriptomic analysis revealed a roughly 100-fold increase in myeloid cell populations enriched with interferon response transcription factors after the second immunization. The study also identified specific innate pathways associated with CD8 T cell and neutralizing antibody responses and demonstrated that monocyte-related features correlated with the neutralizing antibody response to the B.1.351 variant. Overall, these data reveal the immune responses induced by the mRNA vaccine and demonstrate its ability to elicit a stronger innate immune system response upon booster immunization. Figure 3 Changes in antibody and T-Cell responses following BNT162b2 vaccination (Adapted from Arunachalam et al., 2021) Image Caption: a and b show the binding antibody and neutralizing antibody responses after the first and second doses of the vaccine, respectively. The results indicate that most subjects generated an antibody response after the first dose, and the second dose
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