Journal of Vaccine Research 2024, Vol.14, No.6, 307-315 http://medscipublisher.com/index.php/jvr 309 3.2 Long-term observation and durability data of vaccine protection efficacy Long-term studies have shown that the immune response from HPV vaccines lasts for many years. Neutralizing antibodies against both vaccine-covered and some non-vaccine HPV types can still be detected up to 7 years after getting the 2vHPV or 4vHPV vaccine. These antibody levels are expected to stay detectable for even longer (Mariz et al., 2020). In a follow-up from two large clinical trials, researchers found that antibodies against HPV types 6, 16, and 18 were still present up to 12 years after vaccination. People who received the 2vHPV vaccine had much higher antibody levels for HPV 16 and 18 than those who got the 4vHPV vaccine. The 9vHPV vaccine has also shown better long-term protection, especially against HPV types 31, 33, 45, 52, and 58. This makes it more effective than the 2vHPV and 4vHPV vaccines for preventing infections caused by those additional high-risk types. (Figure 2). Figure 2 Comparison of the protective efficacy of the different HPV vaccines (Adopted from Lin et al., 2023) Image caption: Probabilities of vaccine effect on persistent HPV 16 (a), persistent HPV 18 (b), cervical intraepithelial neoplasia grade 2 or worse associated with HPV 16 (c), cervical intraepithelial neoplasia grade 2 or more severe with HPV 18 (d), persistent HPV 31 (e), persistent HPV 33 (f), persistent HPV 45 (g), persistent HPV 52 (h), and persistent HPV 58 (i). The ranking for each vaccine is shown on the cumulative probability plot, with the area under the curve representing the magnitude of the probability. Higher ranking indicates greater efficacy. And vHPV, the valence of human papillomavirus (Adopted from Lin et al., 2023) 3.3 Effectiveness differences in various age groups at the time of vaccination The age at which someone gets the HPV vaccine can affect how well it works. For example, girls between 9 and 15 years old had similar antibody levels whether they got two or three doses. This protection lasted for up to five years (Gilca et al., 2018). This means that two doses might be enough for younger girls. But over time, the two-dose group may not stay as well protected. About two years after the first dose, antibody levels for HPV 16 and 18 started to drop more in girls who only got two doses, compared to those who got all three. In boys, the quadrivalent HPV vaccine has been shown to lower the risk of genital warts and other skin lesions in the genital area. Younger boys had stronger immune responses than older ones, which suggests that getting vaccinated earlier gives better protection (Guo et al., 2024). 4 Safety and Tolerability of the Three HPV Vaccines 4.1 Comparison of common adverse reactions post-vaccination The safety of the bivalent (2vHPV), quadrivalent (4vHPV), and nonavalent (9vHPV) HPV vaccines has been well studied. All three vaccines can cause mild side effects, most commonly at the injection site. These include pain, redness, and swelling, and they usually go away on their own after a short time. Studies have shown that injection-site reactions are slightly more common with the 9vHPV vaccine than with the 4vHPV vaccine
RkJQdWJsaXNoZXIy MjQ4ODYzNQ==