A number of different strains of the human Papillomavirus exist. Some strains can cause cancers of the cervix, vagina, and anus; some can cause genital warts, and some are relatively harmless. A 9-valent vaccine is now available that can protect against nine different harmful strains of the virus; thus, it expands protection beyond that of Cervarix, which protects against two strains and Gardasil, which protects against four strains. A new study by an international team of researchers evaluated the safety and effectiveness of the 9-valent vaccine, Gardasil-9, manufactured by Merck. The findings were published online on June 22 in the journal Pediatrics.
Both Cervarix and Gardasil protect against the two HPV types (HPV-16 and HPV-18) that cause 70% of cervical cancers, 80% of anal cancers, 60% of vaginal cancers, and 40% of vulvar cancers. Gardasil also protects against the two HPV types (HPV-6 and HPV-11) that cause 90% of genital warts.
During its February 2015 meeting, the Advisory Committee on Immunization Practices (ACIP) recommended Gardasil 9 as one of three HPV vaccines that can be used for vaccination of 11- or 12-year-old boys and girls. The ACIP also recommends vaccination for females aged 13 through 26 years and males aged 13 through 21 years who were not previously vaccinated. Vaccination is also recommended through age 26 years for men who have sex with men and for immunocompromised individuals (including those with HIV infection) if not vaccinated previously. Like Gardasil, Gardasil-9 protects against contains HPV 6, 11, 16, and 18; in addition, Gardasil-9 contains protects against HPV 31, 33, 45, 52, and 58. On December 10, 2014, the Food and Drug Administration (FDA) approved Gardasil 9 for use in females aged 9 through 26 years and males aged 9 through 15 years (3).
The authors of the new study note that prophylactic vaccination of young women aged 16 to 26 years with Gardasil-9 prevents infection and disease. The goal of the study was to evaluate the vaccine four use young women to girls and boys aged 9 to 15 years.
The study group comprised 3,066 boys and girls who received a three-dose regimen of Gardasil-9 administered at day 1, month 2, and month 6. Anti-HPV viral assays were conducted at day 1 and month 7. The investigators found that at 4 weeks after dose 3, more than 99% of girls, boys, and young women seroconverted for each vaccine HPV type, meaning that they were protected from infection by nine HPV strains. Increases in titers to HPV types 6/11/16/18/31/33/45/52/58 were found among all vaccine groups. Responses in girls and boys were similar to those of young women. Persistence of anti-HPV effectiveness was demonstrated through 2.5 years after dose 3. Administration of Gardasil-9 was generally well tolerated. A lower number of girls (81.9%) and boys (72.8%) than young women (85.4%) reported injection-site reactions, most of which were of mild to moderate intensity.
The authors concluded that the study demonstrated the safety and effectiveness of Gardasil-9. They recommended that the vaccine should be administered to preadolescents and adolescents.