Here is some general information about the human papilloma virus (HPV) and the HPV vaccines.

What are viruses?

Viruses are very small organisms -- most cannot even be seen with a regular microscope. They cannot reproduce on their own. They must enter a living cell, which becomes the host cell, and "hijack" the cell's machinery to make more viruses.

Viruses can enter the body through the mucous membranes, such as the nose, mouth, the lining of the eyes, or the genitals. They can also enter through breaks in the skin. Once inside, they find their specific type of host cell to infect. For example, cold and flu viruses find and invade cells that line the respiratory tract (nose, sinuses, breathing tubes, and lungs). The human immunodeficiency virus (HIV) infects the T-cells and macrophages of the immune system. HPV infects squamous epithelial cells in the body -- the flat cells that line the surface of the skin and mucous membranes.

What is HPV?

HPV is short for human papilloma (pap-uh-LO-muh) virus. HPVs are a group of over 100 related viruses. Each HPV virus in the group is given a number, which is called an HPV type. HPVs are called papilloma viruses because some of the HPV types cause warts or papillomas, which are non-cancerous tumors. The papilloma viruses are attracted to and are able to live only in squamous epithelial cells in the body. Squamous epithelial cells are thin, flat cells that are found on the surface of the skin, cervix, vagina, anus, vulva, head of the penis, mouth, and throat. HPVs will not grow in other parts of the body.

Of the more than 100 strains of HPV, about 60 HPV types cause warts on non-genital skin, such as on the hands and feet. These are the common warts.

The other 40 HPV types are mucosal types of HPV. "Mucosal" refers to the body's mucous membranes, or the moist skin-like layers that line organs and cavities of the body that open to the outside. For example, the vagina and anus have a moist skin-like layer. The mucosal HPV types are also called the genital (or anogenital) type HPVs because they typically affect the anal and genital area. The mucosal HPVs prefer the moist squamous cells found in this area. They do not grow in the skin of the hands and feet.

Low-risk HPV types

Some types of genital HPVs can cause cauliflower-shaped warts on or around the genitals and anus of both men and women. In women, warts may also appear on the cervix and vagina. This type of "genital wart" is known as condyloma acuminatum and is most often caused by HPV-6 or HPV-11. Because these genital warts rarely grow into cancer, HPV-6 and HPV-11 are called "low-risk" viruses. These low-risk types can also cause low-grade changes in the cells of the cervix that do not develop into cancer.

High-risk HPV types

Other genital type HPVs have been linked with genital or anal cancers in both men and women. These types are called "high-risk" because they can cause cancer. They also cause low-grade and high-grade changes in the cells of the cervix and pre-cancers. Doctors worry more about the high-grade changes and pre-cancers, because they are more likely to grow into cancers. Common high-risk HPV types include:

• HPV-16
• HPV-18
• HPV-31
• HPV-35
• HPV-39
• HPV-45
• HPV-51
• HPV-52
• HPV-58

In summary, low-risk HPV types can cause genital warts and low-grade changes in the cells of the cervix. High-risk HPV types can cause low-grade changes, high-grade changes, pre-cancer, and cancer in the cells of the cervix.

Here is a diagram showing the different groups of HPV types and the problems each group can cause.

How do you get genital HPV?

Genital HPV is spread mainly by direct genital contact during vaginal, oral, or anal sex. It is not spread through blood or body fluids. HPV is passed from one person to another during skin-to-skin contact.

Infection is very common soon after a woman becomes sexually active. In one study, more than 50% of college-aged women were found to have gotten an HPV infection within 4 years of first having sex.

Transmission by genital contact without sexual intercourse is not common, but infection has been reported in women who have never had sex. Oral-genital and hand-genital transmission of some genital HPV types is possible and has been reported. Transmission from mother to newborn during delivery is rare. When it occurs, it can cause warts in the infant's throat called respiratory papillomatosis.

How common is HPV? Who gets it?

Genital HPV is a very common virus. Some doctors think it is almost as common as the common cold virus. In the United States, over 6 million people (men and women) get an HPV infection every year. Almost half of the infections are in people between 15 and 25 years of age. About one-half to three-fourths of the people who have ever had sex will have HPV at some time in their life.

What are the symptoms of HPV?

Genital HPV usually has no symptoms, unless it is a type that causes genital warts. Genital warts may appear within weeks or months after contact with a partner who has HPV. More rarely, genital warts may show up years after exposure.

Most people will never know they have HPV because they have no symptoms and the body's immune system causes the virus to become inactive. In about 90% of cases, the body's immune system clears the HPV infection within 2 years. This is true of both high-risk and low-risk HPV types. A small number of people with HPV will have the virus for a longer time. These people can develop cell changes that over many years may lead to cervical or other genital or anal cancers.

How is HPV related to cervical cancer?

Almost all (more than 99%) cervical cancers are related to HPV. Of these, about 70% are caused by HPV types 16 or 18. About 500,000 pre-cancerous cell changes of the cervix, vagina, and vulva are diagnosed each year in the United States, and over half are related to HPV 16 and 18. Low-grade changes in the cells of the cervix are caused by a variety of HPV types, including 16, 18, 6, or 11. Low-grade changes most often go away without treatment, although if they grow into warts doctors may remove them. But low-grade changes may be caused by some high-risk HPV types (as well as low-risk ones), and doctors who find low-grade changes often do more testing.

Nearly all cervical cancers are related to HPV, but most genital HPV infections do not cause cervical cancer. In research studies, most people who test positive for genital HPV DNA test negative later on, often within 6 to 12 months. Scientists are still not sure whether this means that a person's immune system has completely destroyed all of the HPV or has only suppressed the infection to an extremely low level (too low to be detected by the tests). If even a few cells of the cervix still contain HPV, it's possible that the virus may start to become active again if your immune system becomes very weak.

Changes in the cells of the cervix may suddenly happen many years after being exposed to HPV. These changes may be low-grade or high-grade. This delay could help explain how a woman could have these changes after many years of normal Pap tests and no new sex partner.

If cells stay infected with HPV, the virus may cause the cells of the cervix to change and become pre-cancer cells. True pre-cancer cell changes are called high-grade SIL (squamous intraepithelial lesions), sometimes abbreviated as HSIL. Another term for HSIL is CIN 2 and CIN 3. CIN is an abbreviation for cervical intraepithelial neoplasia.

Pre-cancer cells are not cancer. Some pre-cancer changes may return to normal on their own. But most cases of CIN 3 that are not found and treated are likely to progress to cervical cancer over about 10 years. Still, very few HPV infections lead to cervical cancer. Pre-cancer cells are found before they have a chance to grow into cancer by having regular Pap tests.

For more information on cervical cancer, please see our document, Cervical Cancer.

What about other cancers and HPV?

About 8 out of 10 squamous cell anal cancers are caused by either HPV 16 or 18 -- the same types of genital HPV that cause cervical cancer. A little less than half of cancers of the vulva are HPV-related. Some other genital cancers (cancers of the penis, vagina, vulva, and urethra) and some head and neck cancers (mostly the tongue and tonsils) may be related to the high-risk types of HPV. Also, many of the skin cancers in people with weak immune systems contain the HPV virus.

What about other HPV-related diseases?

Over 500,000 new cases of anal and genital warts are diagnosed yearly in the United States. About 9 out of 10 of these cases are caused by HPV-6 or HPV-11.

Juvenile respiratory papillomatosis occurs in about 1 in 200,000 infants and children. It may lead to breathing problems or rarely progress to cancer of the larynx. It is most often linked with HPV types 6 and 11.

Do men have the kinds of cancers that are related to HPV?

HPV is probably as common in men as in women. But HPV is not as easily diagnosed in men as in women. Genital HPV is mostly passed to men through vaginal and anal sex -- the same way it is in women. Some types of HPV have been linked to cancer of the penis and anus in men. Cancer of the penis is rare, but anal cancer is now almost as common in men and women who have anal sex as cervical cancer was in women before the Pap test was introduced. Even though anal sex greatly raises a person's risk of anal cancer, it is not the only way to get anal HPV or anal cancer.

Like women, men do not have symptoms with HPV unless it is the type that causes genital warts. In men, genital warts can appear around the anus or on the penis, scrotum, groin, or thighs.

There is no test approved to detect HPV in men. But genital warts can be found and treated. While women have the Pap test, there are no tests approved to detect early HPV-related cancers in men. In gay, bisexual, and HIV-positive men, some doctors use anal Pap tests to detect and treat pre-cancerous changes of the anus. Since anal testing is in the early stages of development and use, its effect on anal cancer rates will not be seen for many years.

For more information on sexually transmitted illnesses in men, please contact the American Social Health Organization (ASHA) at www.ashastd.org. You can get information on teen sexual health in English at www.iwannaknow.org or in Spanish at www.quierosaber.org.

Can HPV be treated?

No. Treatments cannot cure HPV. But most genital HPV infections go away with the help of the body’s immune system. About 70% of HPV infections appear to go away within a year and 90% within 2 years. HPV itself cannot be treated, but the cell changes that come from an HPV infection can be treated. For example, genital warts can be treated. Pre-cancer cell changes caused by HPV can be found by Pap tests and treated. And cervical, anal, and genital cancers can be treated, too.

Can HPV be prevented?

The only sure way to prevent HPV is to abstain from all sexual activity. Limiting the number of sex partners and avoiding sex with people who have had many other sex partners decreases a person's risk of exposure to HPV. It is usually not possible to know who has HPV, and HPV infection is so common that even these measures do not guarantee that a person will not get HPV. Still, these measures may help reduce the number of times a person is exposed to HPV.

Condoms provide some, but not total, protection against HPV. The virus can spread during direct skin-to-skin contact before the condom is put on, and male condoms do not cover the entire genital area, especially in women. The female condom covers more of the vulva in women but has not been studied as carefully for its ability to prevent HPV. Condoms are very helpful, though, in protecting from other infections that can be spread through sexual activity.

Getting one of the HPV vaccines before being exposed to HPV will prevent some HPV.

What are the risk factors for genital HPV?

People with the following risk factors are more likely to have genital HPV:

• having many sex partners
• being younger than 25 years of age
• starting to have sex at age 16 or younger
• having a partner who has had many different sex partners

Still, a person who has had sex with only one partner can get HPV if that partner already has the virus. HPV can also be picked up from having sex with an infected person at any age.

Is there a vaccine to prevent HPV?

At this time there are 2 vaccines available to help prevent certain types of HPV and some of the cancers linked to those types: Gardasil^® and Cervarix^®. These vaccines prevent the 2 types of HPV (HPV 16 and 18) that cause 70% of all cervical cancers.

Gardasil also protects against the 2 types of HPV (HPV 6 and 11) that cause 90% of all genital warts. The other types of HPV will NOT be prevented by use of vaccines.

Did the American Cancer Society play a role in the development of the HPV vaccines?

Yes. Dr. Robert Rose at University of Rochester was a member of 1 of 4 teams that contributed to the development of a vaccine against HPV. The grant he received from the American Cancer Society in the mid-1990s enabled him to continue and confirm his important work studying the virus.

Are the HPV vaccines safe?

Gardasil

Before it was approved, Gardasil was tested in more than 21,000 girls and women in many countries around the world. There were no deaths due to the vaccine, and almost no serious side effects reported during those trials. The most common side effect was brief soreness at the injection site. The FDA has determined that this vaccine is safe and effective for females aged 9 to 26 years.

By May 2009, more than 24 million doses of the vaccine had been distributed in the United States. And more than 40 million doses have been distributed world wide. The Centers for Disease Control and Prevention (CDC) and the FDA monitor the safety of all vaccines used in the United States. As of December 31, 2008, the Vaccine Adverse Event Reporting System (VAERS) had received a total of 12,424 reports of potential side effects following HPV vaccination. (VAERS is a national reporting system that monitors reports of potential side effects following vaccination.) About 6% of those reports were serious side effects, about half of the average for vaccines overall.

There have also been 32 cases of death after vaccination reported to VAERS. Each death has been reviewed, and there was no common pattern to the deaths that would suggest they were caused by the vaccine. When there was an autopsy, death certificate, or medical record, the cause of death was explained by factors other than the vaccine. Some causes of these deaths include drug abuse, diabetes, viral illness, blood clots, and heart failure. An unusual neurologic illness caused 2 of the deaths and these deaths are being studies further.

There were also reports of Guillain-Barré Syndrome (GBS) after Gardasil vaccination in the United States. But only some of these have been confirmed as GBS. The CDC says the number of GBS cases reported are well within the range that would be expected to happen anyway (that is, the same number of cases would be expected in people who did not get the vaccine).

Serious blood clots have been reported in a small number of women who received the vaccine. These did not occur in young girls, but instead in teens and young adults. This type of blood clot occurs in a deep vein in the leg, and is known as a deep venous thrombosis (DVT). DVTs are more serious when they travel to one of the blood vessels leading to the lungs. This is known as a pulmonary embolism (PE). Many of the women who had DVTs or PEs after receiving the vaccine had other reasons to get these blood clots. Still, blood clots occurred more often than would be expected. This is being studied further.

Serious allergic reactions are a rare side-effect of most vaccines. The rate of anaphylaxis, the most serious kind of allergic reaction, is not higher after HPV vaccination compared to other vaccines.

Fainting after getting a shot is more common among teens than among young children or adults. It is most often a response to the vaccination process rather than a side effect of the vaccine itself. A U.S. study showed that fainting was not more common after HPV vaccination compared to other vaccines given to teenagers and young women. In order to keep people from getting hurt from fainting, a 15 minute waiting period for people of all ages is recommended after any vaccination.

CDC and FDA doctors and scientists continue to review all reports of serious side effects reported to VAERS to watch for potential new vaccine safety concerns that may need further study. We will monitor those reviews and report any concerns about the safety of the vaccine.

Cervarix

Before it was approved, the safety of Cervarix was tested in almost 24,000 girls and women in many countries around the world. There were no deaths linked to the vaccine. The most common side effects were redness, soreness, and swelling at the injection site. Other complaints included tiredness, headaches, stomach upset, and muscle aches after getting the vaccine--much the same as Gardasil. The FDA has determined that this vaccine is safe and effective for females 10 through 25 years of age.

More than 7 million doses of Cervarix were distributed worldwide as of May 2009.

Like Gardasil, fainting is a risk after getting Cervarix and a 15 minute waiting period is recommended after vaccination.

The Centers for Disease Control and Prevention (CDC) and the FDA will monitor the safety of this new vaccine through the Vaccine Adverse Event Reporting System (VAERS).

Who should be vaccinated and when?

To be most effective, one of the HPV vaccines should be given before a female has any type of sexual contact with another person. Both are given in a series of 3 doses within 6 months.

Here are the American Cancer Society's recommendations for each age group:

• girls ages 11 to 12
  The vaccine should be given to girls ages 11 to 12 and as early as age 9.

• girls ages 13 to 18
  Girls ages 13 to 18 who have not yet started the vaccine series or who have started but have not completed the series should be vaccinated.

• young women ages 19 to 26
  Some authorities recommend vaccination of women ages 19 to 26, but the American Cancer Society experts believed that there was not enough evidence of benefit to recommend vaccinating all women in this age group. We do recommend that women ages 19 to 26 talk to their doctors or nurses about whether to get the vaccine based on their risk of previous HPV exposure and potential benefit from the vaccine.

What about women over 26 years of age? Should they get one of the vaccines?

Women over 26 years of age were not included in the studies that were done to test how well these HPV vaccines worked. This means the FDA could not approve the vaccines for this age group. Studies are now being done in women ages 27 to 55. When those study results are known, a decision can be made about whether to vaccinate women in this age group.

Keep in mind that the risk of HPV exposure is highest soon after women become sexually active. So it is likely that women over 26 have already been exposed to HPV and would not benefit as much from the vaccine.

Are there some girls or women who should not get one of the HPV vaccines or who should wait?

Yes. Anyone who has ever had a life-threatening allergic reaction to yeast or anything else in the HPV vaccines, or anyone who has had a reaction to an earlier dose of HPV vaccine should not get the vaccine. Tell the doctor if the girl getting the vaccine has any severe allergies.

Pregnant women should not get either vaccine. Even though they appear to be safe for both mother and the unborn baby, this still being studied. If a woman who is pregnant does get an HPV vaccine, this is not a reason to consider ending the pregnancy.

Any woman who finds out that she was pregnant when she got the vaccine is encouraged to call the Gardasil vaccine in pregnancy registry at 1-800-986-8999 or the Cervarix vaccine in pregnancy registry at 1-888-452-9622. Information from these registries will help us learn how pregnant women respond to the vaccines. Pregnant women who have started the vaccine series should complete the series after their baby is born.

Women who are breast-feeding may safely get the Gardasil vaccine. Use of Cervarix during breast-feeding has not yet been tested.

Why do the vaccines have to be given at such a young age?

These vaccines will prevent HPV only if they are given before a girl has been exposed to HPV. The vaccines are recommended for girls ages 11 to 12 because most girls at this age have not become sexually active. This is also an age when girls will be seeing their doctor and getting other vaccinations.

Can boys get this vaccine?

In 2009 the FDA approved Gardasil to protect boys from genital warts. Routine vaccination is not recommended, but the vaccine may be offered between ages 9 to 26. It is not yet known if the vaccine will keep boys from passing HPV to their partners, which would also reduce cervical cancer, or if it can prevent HPV-linked cancers in men (such as head and neck or penile cancer).

The American Cancer Society has no recommendation regarding the use of either HPV vaccine in males. But the Society encourages further studies to find out whether HPV vaccines protect against other cancers, along with cervical cancer.

What are the benefits of the vaccines?

Both vaccines will prevent the 2 types of HPV that cause most cervical cancers (about 70%). Gardasil will also protect against the 2 types of HPV that cause most genital warts (about 90%). But they only work in women who have not already been exposed to these types of HPV. They also help prevent vulvar and vaginal cancers related to these 2 types of HPV. The vaccines will not prevent HPV in women who have already had these HPV types.

It is possible that the vaccines also could prevent some other HPV-related cancers, including some cancers of the anus and penis, as well as some head and neck cancers. It will be some years before studies can prove whether they will prevent these cancers.

How long will the vaccines prevent HPV infection?

How long a new vaccine protects people is never known when the vaccine is first introduced. Research is being done to find out how long protection against HPV will last, and if booster vaccines will be needed.

How much does the HPV vaccine cost? Is it covered by health insurance plans?

The drug company price for Gardasil is $130 per dose, and Cervarix is $128 per dose. This cost does not include the cost of giving the shots or the doctor's charge. Insurance plans will likely cover the cost. But check with your insurance plan to know for sure.

The vaccines are included in the federal Vaccine for Children (VFC) program. This program covers vaccine costs for children and teens that don't have insurance and for some children and teens that are underinsured. The VFC program provides free vaccines to children and adolescents younger than 19 years of age, who are either Medicaid-eligible, American Indian or Alaska Native, or uninsured.

There are over 45,000 sites that provide VFC vaccines, including hospitals and private and public clinics. The VFC program also allows children and adolescents to get VFC vaccines through federally qualified health centers or rural health centers if their private health insurance does not cover vaccinations. For more information about the VFC program, visit www.cdc.gov/vaccines/programs/vfc/default.htm. Or call 1-800-CDC-INFO (1-800-232-4636).

Some states and U.S. territories have programs that will cover the vaccine costs, too. You can find the contact information for your area at the CDC Web site given above.

Do you need to be tested for HPV before getting the vaccine?

No. Testing is not needed and it is not recommended. A positive HPV test result does not tell you which types of HPV are present. Even after infection with one type of HPV, the vaccine could still prevent the other types of HPV. A negative test does not tell you if you have had HPV in the past but no longer have it.

Will women and girls who have been vaccinated still need Pap tests?

Yes. People who get vaccinated will still need Pap tests because the vaccine will not prevent all types of HPV that can cause cervical cancer. If your daughter or granddaughter gets the vaccine, she will still need to have Pap tests at the usual times.

If girls who are vaccinated will still need a Pap test, why should they get vaccinated?

The vaccine will actually prevent about 70% of cervical cancers. And those who have had the HPV vaccine can avoid the cervix cell changes caused by the HPV types the vaccine prevents. The Pap test does not keep the cells in the cervix from changing -- it can pick up changes in the cervix after they happen, but before they can become cervical cancer. This means that if a woman has an abnormal Pap test, she will have other tests and then treatment to prevent the cells from becoming cancer. Also, Pap tests are not perfect and can miss cervical changes and cancers.

Can cervical cancer be prevented without a vaccine?

In some cases, yes, cervical cancer can be prevented without a vaccine. Pap tests done according to American Cancer Society guidelines and with proper follow up will prevent most but not all cases of cervical cancer. Pap tests can find cervix cell changes early before they become cervical cancer. These changed cervix cells can then be killed or removed to prevent them from becoming cancer. The Pap test will find most but not all cervical cancers at an early, curable stage. Most cervical cancers in the United States are diagnosed in women who have never had a Pap test, or who haven't had a Pap test in 5 or more years.

If all women who have had sex had regular Pap tests, most cervical cancers could be prevented. Pap tests are used to find changes in the cells of the cervix early so they can be treated before they become cervical cancer.

Is the American Cancer Society in favor of vaccinating against HPV?

Yes, the Society is very much in favor of vaccinating against HPV. The Society has been actively involved in providing credible and unbiased information to the public and to health care providers. The Society emphasizes the ongoing need to follow screening guidelines, such as getting regular Pap tests, and the critical need to ensure that the vaccines are available to the medically underserved.

What is the American Cancer Society doing to promote HPV vaccine use?

The Society is engaged in an active public education effort to ensure broad public awareness and acceptance of these new vaccines. The Society recognizes the importance of building and sustaining the infrastructure to support successful implementation of the vaccine program.

Do you want more information?

For more information on cervical cancer, HPV, HPV testing, and the HPV vaccines, please call us anytime, day or night, at 1-800-227-2345 or visit our Web site at www.cancer.org.

For more information on the HPV vaccines from the Centers for Disease Control (CDC), visit http://www.cdc.gov/vaccines/vpd-vac/hpv/default.htm.

References

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Centers for Disease Control and Prevention. Genital HPV infection - CDC Fact Sheet. Accessed at www.cdc.gov/std/HPV/STDFact-HPV.htm on October 26, 2009.

Centers for Disease Control and Prevention. Human Papillomavirus (HPV) Infection. Accessed at www.cdc.gov/std/hpv/ on October 26, 2009.

Centers for Disease Control and Prevention. Human Papillomavirus (HPV) Vaccine Safety. Accessed at www.cdc.gov/vaccinesafety/updates/human_papillomavirus_vaccine.htm on October 26, 2009.

Centers for Disease Control and Prevention. Reports to the Vaccine Adverse Event Reporting System (VAERS) (September 1, 2009). Accessed at www.cdc.gov/vaccinesafety/vaers/gardasil.htm on October 26, 2009.

Food and Drug Administration: Vaccines, Blood, and Biologics. Approved Products. Cervarix. Accessed at www.fda.gov/BiologicsBloodVaccines/Vaccines/ApprovedProducts/ucm186957.htm on October 16, 2009.

Food and Drug Administration: Vaccines, Blood, and Biologics. Information Pertaining to Labeling Revision for Gardasil. Accessed at www.fda.gov/BiologicsBloodVaccines/Vaccines/ApprovedProducts/ucm165145.htm on October 26, 2009.

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Last Medical Review: 10/28/2009
Last Revised: 10/28/2009