The efficacy of Gardasil nonavalent HPV vaccine

The best choice of HPV vaccine – Gardasil 4vHPV, Cervatrix 2vHPV or Gardasil 9vHPV – will no doubt vary from one country to another. But decisions regarding the relative cost-effectiveness and affordability of a particular vaccine depend upon estimates of its efficacy. As regards the most recent vaccine, Gardasil 9vHPV, Huh & Luxembourg (H&L) have just published the final results of a phase III randomized trial involving nearly 12,000 16-26 year old women in 18 countries over a trial period of 54 months. Because cancer prevention benefits emerge only over the long-term, researchers must rely on various proxies. Previous ecological studies have already attempted to evaluate the impact of vaccination on the basis of declines in infection due to cancer-causing HPV strains (Chow & Fairley/STI; Garland & Jayasinghe/STI), genital warts (Chow & Fairley 2/STI; Ali & Donovan/STI; Wilson & Baker/STI), or HPV specific neoplasia or cytological abnormalities (Paavonen/STI). This randomized, double-blind trial takes account of evidence of all female genital disease, cytological abnormalities and clinical procedures associated with nonavalent HPV types – cervical, vulvar or vaginal. Ethical considerations required the use of Gardasil 4vHPV as a comparator rather than a placebo.

For 9vHPV types not covered by the quadrivalent vaccine (31, 33, 45, 52, 58), H&L report efficacy, as compared with 4vHPV, of: 97.4% for any high-grade disease; 96% for 6-month persistent HPV infection; 100% for cervical neoplasia grade 3; >90% for any grade of cervical or external genital disease, cervical cytological abnormalities or cervical therapy. For 9vHPV types covered by the quadrivalent vaccine, the 9vHPV vaccine showed efficacy in all respects not inferior to the 4vHPV vaccine.

The 9vHPV vaccine is at present licensed in over 60 countries. On the basis of an earlier report from this trial, Durham & Galvani conclude that, for the US, switching entirely to 9vHPV would be cost-effective at all levels of vaccine coverage, and that it would achieve an overall benefit equivalent to an 11% increase in coverage. It should be noted, however, that the trial reported by H&L concerns only the impact of 9vHPV vaccination on female genital disease. It does not investigate the impact of a switch from 4qHPV to 9qHPV either on male (including MSM) anogenital or oropharyngeal disease (Field & Lechner/STI; King & Sonnenberg/STI; Poynten & Grulich/STI), nor, for that matter, its impact on female anal cancers (Sand & Kjaer).