Journal of Vaccine Research 2024, Vol.14, No.6, 307-315 http://medscipublisher.com/index.php/jvr 312 protection. One new vaccine, called Pentarix, targets the E7 proteins from five high-risk HPV types: 16, 18, 31, 45, and 52. These types cause over 80% of all HPV-related cancers. In lab studies, Pentarix has shown strong results. It triggered powerful CD8 T cell responses against multiple HPV types and even helped shrink large tumors in animal models (Ng et al., 2018). Other studies have looked at DNA vaccines that use optimized versions of HPV genes like E6. These vaccines have shown improved immune responses and anti-tumor effects, which means they could be useful for both preventing and treating HPV-related diseases (Oketch et al., 2023). Together, these new approaches represent a big step forward. They could lead to broader, next-generation HPV vaccines that protect against more cancer-causing HPV types (Mason, 2024). 7.2 Joint studies and optimized vaccination schemes for the three vaccines Improving HPV vaccine strategies and working together across countries are key to making vaccines more effective. Mathematical models have helped identify the best ways to use vaccines, especially in low and middle-income countries (LMICs). For example, giving two doses of the vaccine to girls aged 9~14 has been found to be the most efficient and cost-effective option in several LMICs. This approach could even help eliminate cervical cancer in countries like Vietnam, India, and Nigeria. Reviews of cost-effectiveness studies also suggest that gender-neutral vaccination (including boys) and vaccinating multiple age groups at once can improve coverage. However, the cost-effectiveness of these strategies depends on vaccine prices and how many people are getting vaccinated (Walling et al., 2016) (Figure 3). Overall, these findings show that vaccination programs work best when tailored to local needs—and when countries share research and data to guide decisions. Figure 3 Predicted efficiency and cost-effectiveness of different two-dose HPV vaccination strategies targeting girls aged 9~14 years (all strategies are compared with no vaccination) (Adopted from Drolet et al., 2021) 7.3 Challenges in equity and global accessibility in vaccine promotion HPV vaccines work well, but it’s still hard to make sure everyone can get them—especially in developing countries. In places like sub-Saharan Africa, not many people are getting vaccinated. This is mostly because of high costs, not enough vaccine supply, and low public awareness (Drolet et al., 2021). Still, studies show that things like education and involving local communities can help increase vaccination rates. When people learn more about HPV and local leaders support the vaccine, more families are willing to get their children vaccinated. Also, new research suggests that just one dose of the HPV vaccine might give strong, long-lasting protection. This could be a big help in low-income areas where many girls don’t get vaccinated at all (Tang et al., 2022). To fix these issues, countries and global health organizations need to work together. They should focus on making the vaccine cheaper, easier to get, and use clear messages to help people understand why it's important. 8 Concluding Remarks Comparing the bivalent (2v-HPV), quadrivalent (4v-HPV), and nonavalent (9v-HPV) vaccines shows clear differences in how well they protect against different HPV types. The 9v-HPV vaccine is the most effective at preventing infections from HPV types 31, 33, 45, 52, and 58. In contrast, the 2v-HPV and 4v-HPV vaccines offer limited cross-protection, mostly against HPV 31.
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