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UC Davis Comprehensive Cancer Center

UC Davis Comprehensive Cancer Center

Learn more about the human papillomavirus (HPV)

Questions and answers


The human papillomavirus (HPV) is from the family of papilloma viruses that infect human cells. Considered one of the most powerful human carcinogens, HPV is the cause of 5% of all cancers. There are more than 100 types of HPV; 13 of them are responsible for cervical, vaginal, vulvar, anogenital and oropharynx cancers. HPV 16 is responsible for the majority of HPV-associated cancers.



Those most susceptible to HPV-related cancer are:

  • People with compromised immune systems such as those with HIV or organ transplant recipients
  • Smokers
  • People who engage in high-risk sexual behavior or have numerous sexual partners



The HPV 16 and 18 strains are known to cause cervical cancer.





cancer cells

Progression depends on the type of HPV strain and on the unique characteristics of the individual who is infected. The longer the virus is present, the higher the potential for a cancer to develop. The good news is that more than 90% of HPV 16 and 18 infections go away within 6 to18 months of initial exposure.



HPV is the most common sexually transmitted disease. About 20 million Americans are infected. Most sexually active men and women will be exposed to HPV at some point during their lifetime. In the U.S. HPV causes 18,000 cancers in females each year, and 7,000 cancers in men. The virus is especially prevalent in regions with high rates of cervical cancer such as Sub-Saharan Africa, India and Latin America.

couple holding hands

HPV is passed through genital (skin-to-skin) contact, most often during vaginal or anal sex. HPV also can be passed on during oral sex. Most people never even know they have HPV, or that they are passing it to a sexual partner. So it may not be possible to know who gave you HPV or when. HPV is so common that most people get it soon after they start having sex. All women who have had sex are at risk for HPV and cervical cancer.

Cancer cell

HPV gets into the body through tiny scrapes on the skin. Once it reaches the basal layer of the epithelial cells the virus replicates and causes changes to the normal cervical cell, transforming it into a cancer cell.





Whether a woman clears the virus depends on her immune response and the ability of the virus to evade the immune response and reproduce.




pap smear test

Experts recommend HPV testing for women who are:

  • Age 30 or older — as part of regular screening, with a Pap test, or
  • Age 21 or older — for follow-up of an abnormal Pap test result.




HPV is very common in women under age 30 and most of these women will fight off the virus within a few years and never experience health problems as a result of HPV. HPV is less common in women over age 30 and its presence is more likely to signal a health concern. Your doctor can use the results of the HPV test and the Pap test to determine if you need to be more closely followed to look for cervical cancer.

There is currently no FDA-approved screen of HPV for men.


When a doctor finds the HPV DNA, it may signal cervical cancer and prompt further screening. The DNA test also can determine whether the woman is at high or low risk of invasive cancer.





There are two types of HPV vaccine. Gardasil protects against HPV 6, 11, 16 and 18. Cevarix protects against HPV 16 and 18.





The vaccine uses particles from the HPV to cause the immune system to recognize the HPV if and when infected. The vaccine prevents normal cervical cells from becoming cancer cells.




The vaccine does not treat HPV infections, so it should be obtained prior to initiation of sexual activity when it is most effective in preventing infection. After a woman engages in sexual activity she is much more likely to be exposed to one or more strains of HPV.




In a pivotal randomized trial, Guardasil prevented 98 percent of cervical cancers in women not previously exposed to HPV, and 44% in women with an active HPV 16 or 18 infection. Studies showed a 93% efficacy rate for Cevarix.



The vaccine can cause pain, redness and itching at the site of the shot. The vaccine may also cause a mild fever, which goes away on its own. Guillain-Barré Syndrome (GBS), which is a rare disorder that causes muscle weakness, has been reported. To date, there is no evidence that Gardasil causes GBS. People have reported blood clots after getting Gardasil.

Three doses are required. The second should be given two months after the first; the third at six months.

A study published in the Journal of the American Medical Association in 2013 showed that two doses are as effective as three, but the immune response may not last as long with two doses.

Booster vaccines are not recommended at this time.

With either vaccine, the cost is about $130 per dose.

Guardasil is covered for both girls and boys through the Vaccines for Children Program.


In June 2006, the federal Advisory Committee on Immunization Practices recommended HPV vaccine for 11- to 12-year-old girls and young women through age 26 who hadn't already received the vaccine.





In October 2009, the advisory committee recommended routine 3-dose vaccination of males aged 11 or 12 years to prevent HPV infection and HPV-related disease. They recommended that the vaccination could begin as young as age 9 and that boys and young men 13 to 21 years of age who hadn't already received the vaccine should also be vaccinated.

Sources: Jyoti Mayadev, Assistant Professor, Radiation Oncology and Edwin Alvarez, Assistant Professor, Gynecology Oncology