HPV Vaccine Strain Coverage
The currently available HPV vaccine in the United States is the 9-valent vaccine (Gardasil-9), which covers 9 HPV strains: types 6,11,16,18,31,33,45,52, and 58. 1
Evolution of HPV Vaccine Coverage
The HPV vaccine landscape has evolved significantly over time:
Historical Vaccines (No Longer Available in US)
- Bivalent vaccine (Cervarix): Covered 2 strains - HPV types 16 and 18 1, 2
- Quadrivalent vaccine (Gardasil): Covered 4 strains - HPV types 6,11,16, and 18 1
Current Vaccine (As of January 2017)
- 9-valent vaccine (Gardasil-9): The only HPV vaccine available in the United States, covering 9 strains 1
Strain-Specific Protection
The 9-valent vaccine provides protection against:
Cancer-causing (high-risk) types:
- HPV 16 and 18: Responsible for approximately 70% of cervical cancers worldwide 1, 2
- HPV 31,33,45,52, and 58: Responsible for an additional 14% of HPV-related cancers in women and 4% in males 1
Genital wart-causing (low-risk) types:
- HPV 6 and 11: Responsible for 90% of genital warts 1
Clinical Impact of Expanded Coverage
The 9-valent vaccine's expanded coverage represents a significant advancement:
- Total cancer prevention: The 9 strains collectively protect against approximately 84% of HPV-related cancers in women (70% from types 16/18 plus 14% from the five additional types) 1
- Efficacy: The vaccine demonstrated 97% efficacy in preventing cervical, vulvar, and vaginal cancer precursor lesions related to the five additional types (31,33,45,52,58) 1
- Non-inferior protection: Antibody response against the original 4 types (6,11,16,18) in the 9-valent vaccine was non-inferior to the quadrivalent vaccine 1
Important Caveats
The vaccine does not cover all cancer-causing HPV types. While high-risk types 16,18,31,33,35,39,45,51,52,56,58,59,68,69,73, and 82 can cause cervical cancer, the 9-valent vaccine only covers 7 of these types 1. Therefore, cervical cancer screening remains essential even in vaccinated individuals 1.