Nine-valent usually refers to the nine-valent HPV vaccine, which was approved for marketing in the U.S. in 2014, and has only been available for eight years, and clinical studies on its expiration date exist and do not validate whether it is effective for life. There are currently two clinical studies following up vaccinated subjects to evaluate the long-term safety, immunogenicity, and protective effect of the vaccine against cervical disease. One study, Study 1, followed up to 7.6 years after the third dose of vaccination, found no cases of HPV6, 11, 16, 18, 31, 33, 45, 52, and 58-associated high levels of intraepithelial neoplasia of the cervix. Study 2 was followed up for 6.4 years and also found no cases of highly intraepithelial neoplasia. Vaccinated patients also need to be monitored for physical symptoms and have regular medical checkups.