Expanded strain coverage for a highly successful public health tool: Prophylactic 9-valent human papillomavirus vaccine.

Human papillomavirus is considered the causative factor for cervical cancer, which accounts for approximately 5% of the global cancer burden and more than 600,000 new cases annually that are attributable to HPV infection worldwide. The first-generation prophylactic HPV vaccines, Gardasil® and Cervarix®, were licensed approximately a decade ago. Both vaccines contain the most prevalent high-risk types, HPV16 and 18, which are associated with 70% of cervical cancer. To further increase the type coverage, 5 additional oncogenic HPV types (31, 33, 45, 52 and 58) were added to the existing Gardasil-4 to develop a 9-valent HPV vaccine (9vHPV), Gardasil 9®, increasing the potential level of protection from ∼70% to ∼90%. The efficacy of the vaccine lies primarily in its ability to elicit type-specific and neutralizing antibodies to fend off the viral infection. Therefore, type-specific and neutralizing murine monoclonal antibodies (mAbs) were used to quantitate the antigenicity of the individual vaccine antigens and to measure the antibody levels in the serum samples from vaccinees in a type- and epitope-specific manner in a competitive immunoassay. Assays for 9vHPV are extended from the proven platform used for 4vHPV by developing and adding new mAbs against the additional types. In Phase III clinical trials, comparable safety profile and immunogenicity against the original 4 types were demonstrated for the 9vHPV vaccine, and these were comparable to the 4vHPV vaccine. The efficacy of the 9vHPV vaccine was established in trials with young women. Immunobridging for younger boys and girls was performed, and the results showed higher immunogenicity in the younger age group. In a subsequent clinical trial, the 2-dose regimen of the 9vHPV vaccine used among girls and boys aged 9-14 y showed non-inferior immunogenicity to the regular 3-dose regimen for young women (aged 16-26 years). Overall, the clinical data and cost-effectiveness analysis for the 9vHPV vaccine support its widespread use to maximize the impact of this important, life-saving vaccine.