Journal of Vaccine Research 2024, Vol.14, No.6, 307-315 http://medscipublisher.com/index.php/jvr 308 other cancers. There are many types of HPV, and among them, HPV 16 and 18 are the most likely to cause cancer. HPV vaccines work by helping the body make neutralizing antibodies. These antibodies target the virus’s L1 protein, which forms the outer shell of the virus. The vaccines don’t contain live virus. Instead, they use virus-like particles (VLPs) that look like the real virus but can't cause infection. This makes them safe and effective at triggering the immune system to respond (Wang et al., 2019). 2.2 HPV types covered by bivalent, quadrivalent, and nonavalent vaccines and their corresponding diseases The bivalent vaccine (2v-HPV) protects against HPV types 16 and 18. These two types are linked to most cervical cancer cases. The quadrivalent vaccine (4v-HPV) includes HPV types 6, 11, 16, and 18. In addition to preventing cervical cancer, it also protects against genital warts caused by types 6 and 11. The nonavalent vaccine (9v-HPV) covers nine HPV types in total: 6, 11, 16, 18, 31, 33, 45, 52, and 58. This vaccine gives wider protection, including more high-risk types that can lead to cervical and other cancers (Faust et al., 2016). 2.3 Analysis of the indications of each vaccine in preventing cervical cancer, genital warts, and other diseases The bivalent vaccine is mainly used to prevent cervical cancer and related precancerous conditions. It targets the two most dangerous HPV types (16 and 18).The quadrivalent vaccine also helps prevent cervical cancer but offers extra protection against genital warts, thanks to the inclusion of HPV types 6 and 11. The nonavalent vaccine gives the broadest protection. It can prevent most cases of cervical cancer, genital warts, and other cancers related to HPV. This makes it a strong choice for wider public health coverage (Mühr et al., 2022).(Figure 1). Figure 1 Premises and advantages of DNA-based, therapeutic anti-HPV vaccines (Adopted from Tang et al., 2022) 3 Comparison of Immunogenicity and Durability of the Three HPV Vaccines 3.1 Immune response effectiveness of the three vaccines in different populations The immune response from the bivalent (2vHPV), quadrivalent (4vHPV), and nonavalent (9vHPV) vaccines can be different depending on the group of people. Studies show that the 9vHPV vaccine usually gives stronger and broader protection than the other two. For example, it causes almost 100% of people to develop antibodies against HPV types 31, 33, 45, 52, and 58. This high level of protection stays strong even 24 months after the first shot (Godi et al., 2019). The 2vHPV and 4vHPV vaccines don’t protect as well against types they don’t directly target, and their antibody levels go down over time. But the 2vHPV vaccine creates higher peak antibody levels for HPV 16 and 18 than the 4vHPV vaccine. It also tends to trigger stronger cross-protection for some other HPV types. Interestingly, combining one dose of the 9vHPV vaccine with one dose of the 2vHPV vaccine has also been found to work well. This mixed schedule was safe and gave 100% antibody coverage for all nine HPV types included in the 9vHPV vaccine.
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