All About HPV

Autor: Christina Bach, MBE, LCSW, OSW-C
Contribuidor de contenido: Lara Bonner Millar, MD and Carolyn Vachani, RN, MSN, AOCN
Fecha de la última revisión: December 27, 2022

What is HPV?

Human papillomaviruses (HPV) are common viruses named for their ability to cause warts, also known as papillomas. There are more than 200 types (or strains) of HPV. About 40 of these strains can be spread through sexual contact. Most strains of HPV do not cause problems. However, several can cause genital warts and 12 types are known to cause cancer. Genital HPV infection is very common, affecting about 80 million Americans in their lifetime. Sexually active individuals have an 80-85% chance of being infected with HPV at some point in their lives.

HPV can infect the skin, genitals, and oropharynx (mouth/throat), and spread through genital skin-to-skin contact, masturbation, and oral, vaginal, or anal sex with another person (of either sex) who has HPV. A person who has HPV will usually not have any symptoms from the virus. Many people do not know that they are infected. It is important to know that the great majority of infections with high-risk HPV go away on their own (they are cleared by the immune system, usually within 2 years), and therefore do not lead to cancer.

Am I at Risk for HPV Infection?

Risk factors include

  • Sexual activity. Vaginal intercourse and anal penetration appear to be the easiest ways to spread the infection, but they are not necessary to transmit the virus. Genital skin-to-skin contact and oral sex can spread the virus as well. Masturbation with a partner may even be sufficient to transmit the virus as HPV can be detected on the fingertips of women and men who have genital warts.
  • Having many sexual partners (or a partner with a history of many sexual partners).
  • Early age at first intercourse (vaginal or anal).
  • History of other sexually transmitted infections.

High-Risk Versus Low-Risk Strains of HPV

The different strains of HPV are classified as either low-risk or high-risk.

  • Low-risk HPV (including HPV types 6 and 11) can cause genital warts—or no symptoms at all.
  • High-risk HPV (including HPV types 16 and 18) causes of about 70 percent of cervical cancers.
    • Infection with high-risk HPV may or may not cause symptoms.

What Cancers Can Be Caused by HPV?

  • Cervical cancer.
  • Vaginal cancer.
  • Vulvar cancer.
  • Anal cancer.
  • Head and Neck cancer- in particular within the oropharynx (areas in the back of the mouth, the base of the tongue, and the tonsils).

Clearing the Infection

We don't know why some people's immune systems can clear the HPV infection and others cannot. We do know that smoking is one thing that increases the chance that the immune system will not clear the virus. Other factors in women (as this is the population in whom most of the research has been done) include multiple childbirths, long-term oral contraceptive use, and possibly chronic inflammation, though we don't know exactly why these factors increase risk.

Because most people's immune systems are able to clear the virus, the risk of transmission may be lower for couples who wait longer to have sexual relations or have long periods of abstinence between relationships, thus giving their bodies time to clear any infection before entering a new sexual relationship. Risk is lower for long-term, monogamous couples as well. In general, HPV infection lasts about 1 year in women and may be as short as 6 months in men, but this may vary depending on the strain. Shorter gaps between relationships may allow the infection to hop between partnerships, whereas longer periods of abstinence allow the infection to clear between sexual encounters.

The large majority (more than 90%) of infections will clear on their own, but people with active infections that persist after 2 years are at the highest risk of progression to cancer. The key is that these women (as we do not currently test for HPV in cis men) need to be vigilant with follow-up and annual Pap testing to enable any pre-cancerous changes to be detected early when they are easiest to treat.

Prevention: HPV Vaccines

The HPV vaccine protects against infection by certain strains of HPV that can cause cervical, vaginal, vulvar, and anal cancer and genital warts. There are 3 HPV vaccines produced, though, in the United States, only Gardasil 9 is available.

  • Ceravix protects against HPV 16 & 18.
  • Gardasil protects against HPV strains 16, 18, 6 & 11.
  • Gardasil 9 protects against HPV 6, 11, 16, 18, 31, 33, 45, 52, and 58.

This vaccine does not treat cancer. Females who receive the vaccine should still undergo Pap testing as recommended by their provider because it does not protect against all types of HPV. HPV-16 and HPV-18, are responsible for most cases of cervical cancer. HPV-6 and HPV-11, cause about 90% of genital warts.

HPV vaccines are recommended for all individuals ages 12-26. It is given in 2 or 3 doses, depending on the age you are when it is started. The US Food & Drug Administration has approved the vaccine for use in individuals up to age 45, though most insurance companies will not cover it beyond age 26 and it is not recommended for routine use after age 26 by any professional organizations. The most common side effects after the injection are fainting, dizziness, nausea, headache, and skin reactions at the site where the shot was given.

While the HPV vaccine is believed to prevent cervical cancer, because the strains that cause cervical cancer also cause other forms of cancer, it is estimated that 49% of vulvar cancers, 55% of vaginal cancers, and 79% of anal cancers may be prevented by vaccination against HPV-16 and 18.

It is important to remember that the HPV vaccine does not protect against all types of HPV or other sexually transmitted infections, such as HIV.

HPV Screening and Cancer Prevention

Cervical cancer is the second most common cancer in women worldwide, with about 500,000 new cases per year, most in developing countries. There are an estimated 13,000 cases diagnosed in the US every year. Screening with Pap testing has resulted in dramatically lower rates of cervical cancer in many developed nations, but countries with fewer resources lag far behind in lowering the incidence of this disease.

The HPV vaccine does not protect against all types of HPV that lead to cervical cancer, therefore women should still receive regular screening, even after receiving the vaccine.

The American Cancer Society recommends the following guidelines for cervical cancer screening:

  • All women should begin cervical cancer screening at age 25.
  • Women between the ages of 25 and 65 should have:
    • Primary HPV testing every 5 years. This test is not yet available at many centers/practices.
    • If this test is not available, you should be screened with co-testing, which is a combination of an HPV and Pap test. This should be done every 5 years.
    • If HPV testing is not available, then a Pap test alone should be performed every three years.
  • Women over age 65 who have had regular cervical screenings that were normal should not be screened for cervical cancer.
  • Women who have been diagnosed with cervical pre-cancer should continue to be screened until they meet one of the following criteria over the previous 10 years:
    • Two negative, consecutive HPV tests.
    • Or 2 negative, consecutive co-tests.
    • Or 3 negative, consecutive pap tests in the last 3-5 years.
  • Women who have had their uterus and cervix removed in a hysterectomy and have no history of cervical cancer or pre-cancer should not be screened.
  • Women who have had the HPV vaccine should still follow the screening recommendations for their age group.
  • While the ACS does not recommend cervical cancer screening every year, women should still see their provider for a well-woman checkup.

Women who are at high risk for cervical cancer may need to be screened more often. Women at high risk might include those with HIV infection, organ transplant, or in-utero exposure to the drug DES. They should talk with their doctor or nurse for specific recommendations.

There is no approved screening test to find early signs of penile, vulvar, head-and-neck, or anal cancer. Routine examination of these areas and reporting of any changes to your provider is recommended. However, as previously mentioned, men who engage in receptive anal intercourse or women with cervical dysplasia or HIV may benefit from anal pap screening. Learn more about this screening on the UCSF anal neoplasia research & treatment group website.

Talk with your provider about HPV testing, vaccines, and cancer risk reduction.

Resources for More Information

  • American Cancer Society. Cervical Cancer. 2017. Found at:
  • Burchell AN, Tellier PP, Hanley J, Coutlée F, Franco EL. Influence of partner's infection status on prevalent human papillomavirus among persons with a new sex partner. Sexually Transmitted Diseases 37: 34-40, 2010.
  • Burchell, AN. Transmission of HPV: A brief timeline. Cervical Cancer Prevention. Cervical Cancer Prevention: In Press
  • Centers for Disease Control and Prevention. HPV Information
  • Centers for Disease Control and Prevention. How many cancers are linked with HPV each year? March, 2017. Found at:
  • De Vuyst H, Clifford G, Nascimento MC, et al. Prevalence and type distribution of human papilomavirus in carcinoma and intraepithelial neoplasia of the vulva, vagina, and anus: A meta-analysis. Int J Cancer 124:1626-1636, 2009.
  • FDA Access Data Cervarix.
  • FDA Access Data. Gardasil.
  • FDA Access Data. Gardasil 9.
  • Ganguly, N; Parihar, SP. Human papillomavirus E6 and E7 oncoproteins as risk factors for tumorigenesis. J Biosci 34 (1): 113–23, 2009.
  • Gillison ML. Human papillomavirus and prognosis of oropharyngeal squamous cell carcinoma: implications for clinical research in head and neck cancers". J. Clin Oncol 24 (36): 5623–5, 2006.
  • National Cancer Institute. HPV and Cancer. 2019. Retrieved from:
  • National Cancer Institute. Human Papilomavirus Vaccines. 2018. Retrieved from:
  • Ringström E, Peters E, Hasegawa M, et al. Human papillomavirus type 16 and squamous cell carcinoma of the head and neck. Clin Cancer Res 8 (10): 3187-92, 2002.
  • Palefsky J and Rubin M. The Epidemiology of anal human papillomavirus and related neoplasia. Obstet Gynecol Clin N Am 36:187-200, 2009.
  • Plummer M, Schiffman M, Castle PE, et al. A two-year prospective study of human papillomavirus persistence among women with a cytological diagnosis of atypical squamous cells of undetermined significance or low-grade squamous intraepithelial lesion. JID. 2007;195:1582-1589.
  • Schwartz SR, Yueh B, McDougall JK, et al. Human papillomavirus infection and survival in oral squamous cell cancer: a population-based study. Otolaryngol Head Neck Surg 125 (1): 1-9, 2001.
  • Tobian AA, Serwadda D, Quinn TC, et al. Male circumcision for the prevention of HSV-2 and HPV infections and syphilis. N Engl J Med. 360(13):1298-309, 2009.
  • UCSF Anal Dysplasia Clinic website

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