Of the more than 200 types of human papillomavirus (HPV), only 12 are classified as high-risk for cancer: HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59. Among these, HPV 16 and 18 are responsible for the vast majority of HPV-related cancers, causing roughly 76% of all cervical cancers worldwide. The remaining high-risk types each contribute a smaller share, but collectively they account for a significant portion of cases.
HPV 16 and 18: The Most Dangerous Types
HPV 16 is the single most oncogenic type. It dominates cervical cancer statistics and is even more concentrated in throat cancers, accounting for approximately 95% of HPV-positive oropharyngeal cancers. HPV 18 is the second most common cancer-causing type and tends to drive a more aggressive form of cervical cancer called adenocarcinoma, which develops in glandular cells rather than the flat cells lining the cervix.
Together, these two types cause about three out of every four cervical cancers globally. They’re also the primary drivers behind most other HPV-related cancers at different body sites. Every licensed HPV vaccine in the world protects against both of them.
The Other High-Risk Types
The remaining ten high-risk types (31, 33, 35, 39, 45, 51, 52, 56, 58, and 59) each carry a lower individual risk than 16 or 18, but they still cause real cancers. HPV 45, for example, is the third most common type found in cervical cancers. Types 31, 33, 52, and 58 are notable because they’re included in the nine-valent vaccine (Gardasil 9), which covers HPV 6, 11, 16, 18, 31, 33, 45, 52, and 58. FDA-approved screening tests can detect up to 14 high-risk types, including all 12 listed above plus types 66 and 68, which are sometimes classified as “probably” carcinogenic.
Low-Risk Types Don’t Cause Cancer
HPV types 6 and 11 are the most well-known low-risk types. They cause about 90% of genital warts but are not linked to cancer. Warts from these types can be uncomfortable and recurrent, but they don’t transform into malignant tumors. The distinction matters because a positive HPV test result doesn’t automatically mean cancer risk. Only testing that identifies high-risk types provides meaningful information about cancer.
Cancers Caused by High-Risk HPV
HPV doesn’t just cause cervical cancer. High-risk types, especially HPV 16, drive cancers at several body sites:
- Cervical cancer: Nearly all cases are caused by HPV. Types 16 and 18 account for about 76%.
- Anal cancer: Roughly 90% of anal squamous cell cancers are attributed to HPV. Risk is particularly elevated in people with HIV.
- Oropharyngeal cancer (throat, base of tongue, tonsils): HPV is found in about 45% of these cancers in men, with HPV 16 responsible for the overwhelming majority.
- Penile cancer: About 48% of cases are HPV-positive.
- Vulvar and vaginal cancers: A substantial share are HPV-driven, though the exact percentage varies by tumor type.
One striking trend: in several high-income countries including the U.S., U.K., France, and Switzerland, HPV-related throat cancer in men now occurs more frequently than cervical cancer in women. Cervical cancer rates have dropped thanks to screening and vaccination, while oropharyngeal cancer rates in men continue to climb with no established screening program to catch them early.
How High-Risk HPV Turns Cells Cancerous
High-risk HPV types produce two proteins that essentially disable your cells’ built-in cancer defenses. One protein targets p53, a molecule your cells rely on to detect DNA damage and trigger self-destruction before damaged cells can multiply. The viral protein hijacks a normal cellular process, tagging p53 for disposal so the cell can no longer recognize when something has gone wrong. The second protein disables a different safeguard that controls when cells are allowed to divide. With both brakes removed, infected cells can accumulate genetic damage and divide uncontrollably.
Low-risk HPV types produce versions of these same proteins, but their versions bind weakly to these cellular targets. That’s why low-risk types can cause cell growth (warts) but don’t lead to cancer.
Most Infections Never Become Cancer
Even with a high-risk type, cancer is not the likely outcome. Between 80% and 90% of all HPV infections clear on their own within two years. The immune system eliminates the virus without any treatment, and the infected person typically never knows they had it. About 43% of infections clear within just six months, with a median duration of roughly seven and a half months.
The infections that matter are the ones that persist. When high-risk HPV lingers for years, it has more time to drive the genetic changes that lead to precancerous lesions. In women diagnosed with advanced precancerous cervical changes, about 31% developed invasive cancer within 30 years if left untreated. That long timeline is actually good news: it means screening can catch problems well before they become cancer. Factors that increase the chance of an infection persisting include a weakened immune system (particularly from HIV), smoking, and long-term use of oral contraceptives.
Screening and Vaccination Coverage
Current screening recommendations from the American Cancer Society call for HPV testing starting at age 25, repeated every five years through age 65. The U.S. Preventive Services Task Force offers a few options for people aged 30 to 65: an HPV test every five years, a combined HPV and Pap test every five years, or a Pap test alone every three years. These guidelines apply to cervical cancer screening. No equivalent screening exists for HPV-related throat, anal, or penile cancers in the general population.
The nine-valent vaccine covers the two types that cause most genital warts (6 and 11) plus seven high-risk cancer types (16, 18, 31, 33, 45, 52, and 58). That combination protects against the HPV types responsible for the large majority of HPV-related cancers across all body sites. Vaccination is most effective when given before any exposure to HPV, which is why it’s recommended in the preteen years, but it’s approved for people up to age 45.