International Journal of Clinical Case Reports 2024, Vol.14, No.3, 117-131 http://medscipublisher.com/index.php/ijccr 119 delivery methods to minimize these adverse effects while maintaining strong immunogenicity (Chu et al., 2021; Sharif et al., 2021). Additionally, long-term safety data are still being collected, and continuous monitoring is essential to ensure the vaccines' safety over extended periods (Knezevic et al., 2021; Sahly et al., 2021). Figure 1 Main delivery methods for mRNA vaccines (Adapted from Wang et al., 2021) 3 Efficacy of mRNA Vaccines 3.1 Efficacy in preventing COVID-19 mRNA vaccines have demonstrated high efficacy in preventing COVID-19 across various clinical trials. The BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccines have shown efficacy rates of 95% and 94.1%, respectively, in preventing symptomatic COVID-19 in large-scale randomized controlled trials (Baden et al., 2020; Polack et al., 2020; Graña et al., 2022). These vaccines have been effective in reducing the incidence of symptomatic COVID-19 compared to placebo, with high-certainty evidence supporting their use (Graña et al., 2022). Additionally, the mRNA-1273 vaccine has shown a 98.2% efficacy in preventing severe or critical COVID-19, further underscoring its effectiveness in mitigating the disease's impact (Graña et al., 2022). Real-world data also support the high efficacy of mRNA vaccines. A study involving healthcare personnel, first responders, and other essential workers found that the BNT162b2 and mRNA-1273 vaccines were 90% effective in preventing SARS-CoV-2 infection, regardless of symptom status (Thompson et al., 2020). This evidence highlights the robust protection offered by mRNA vaccines in both clinical trial settings and real-world conditions. 3.2 Comparison of efficacy across populations The efficacy of mRNA vaccines has been consistent across different populations, including various age groups and individuals with comorbidities. For instance, the BNT162b2 vaccine has shown similar efficacy rates across subgroups defined by age, sex, race, ethnicity, baseline body-mass index, and the presence of coexisting conditions (Polack et al., 2020). This broad efficacy profile suggests that mRNA vaccines are effective in diverse demographic groups.
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