A Look at Each Vaccine: Human Papillomavirus

View a list of questions submitted by readers on our companion web page at prevent-hpv.org.

The disease

What is human papillomavirus?

Human papillomavirus (HPV) is a virus that infects the skin, genital area and lining of the cervix. There are many different types of papillomaviruses (about 100). Some types of papillomaviruses cause warts on the skin, some types cause warts in the anal and genital areas, and some types cause cervical cancer.

Many different HPV types cause cervical cancer. Two types (16 and 18) are the most common, accounting for about 7 of every 10 cases of cervical cancer. Similarly, many types of HPV cause anal and genital warts; but only two types (6 and 11) account for about 9 of every 10 cases.

The HPV vaccine, known as GARDASIL®, protects against nine types of HPV that cause disease in people. The types in the vaccine are 6, 11, 16, 18, 31, 33, 45, 52, and 58.

Other viruses can cause cancer, too. For example, hepatitis B virus can cause liver cancer, AIDS virus can cause sarcoma (cancer of skin and soft tissues), and Epstein-Barr virus (the virus that causes 'mono') can cause cancers of the head and neck and of the immune system. These types of cancers can also be caused by other things. For example, alcohol can cause liver cancer, the sun can cause skin cancer, and poisons can cause cancer of the immune system.

Cervical cancer is unique in that it has only one cause: HPV.

How common is HPV?

HPV is the most common sexually transmitted disease in the United States and in the world. Twenty million Americans are currently infected with HPV and an additional 6 million Americans are infected every year. Half of those newly infected with HPV are between 15 and 24 years of age.

Is HPV dangerous?

Yes. Although most HPV infections typically resolve on their own, some persist. Every year in the United States:

  • About 34,000 HPV-associated cancers occur:
    • More than 20,000 of these are in females
    • Almost 14,000 are in males
  • The most common types of cancer caused by HPV infections are cervical cancer and head and neck cancers:
    • About 10,800 cases of cervical cancer and 4,000 deaths occur annually
    • About 10,700 males and 2,200 females are diagnosed with cancers of the head and neck
  • Babies can also be infected when they pass through the birth canal of a mother infected with HPV. Some of these children go on to develop a long-term infection of their windpipe that is occasionally fatal. This disease is called recurrent respiratory papillomatosis.

How do you catch HPV?

HPV is transmitted from one person to another by genital contact. Although this most often occurs during sexual intercourse, it can also occur during oral or anal sex or through genital-to-genital contact in the absence of sexual intercourse.

HPV infections are unique. First, most people never know they were infected. Unlike a cold in which symptoms develop a few days after exposure to the virus, HPV infections are typically not symptomatic. Second, HPV infections can last for long periods of time. The average length of infection is about eight months; however, for about 1 of every 10 women, the infection lasts longer than two years. It is in this group of women that there is an increased risk of developing cervical cancer. Cervical cancer often doesn’t occur until 20 years after the initial infection.

How can you avoid getting HPV?

Sometimes people can be infected with HPV and not know it. So HPV can be difficult to avoid. The best way to avoid genital infection with HPV is abstinence. You can also decrease your chance of getting HPV by having sex with only one other person who isn't infected with HPV. While condoms may also decrease the chance of getting HPV, they do not always work to prevent the spread of the infection. Because other than abstinence, none of these measures can completely protect someone from becoming infected or prevent the spread of this infection, the development of a vaccine was an important tool for preventing future generations from experiencing the devastation caused by HPV.

Can't I avoid cervical cancer by simply getting routine Pap testing?

No. At one time cervical cancer was the most common cause of cancer in the United States. One test changed that: the Papanicolaou (Pap) test. The Pap test is performed by scraping cells from the opening of the cervix and examining them under the microscope to see whether they have begun to show changes consistent with the early development of cancer (called pre-cancerous changes). Typically, the length of time from infection with HPV to development of cervical cancer is about 15-20 years. For this reason, although most HPV infections occur in teenagers and young adults, cervical cancer is more common in women in their 40s and 50s.

The Pap test is one of the most effective cancer screening tests available and has dramatically reduced the incidence of cervical cancer in the United States. But the test isn't perfect and not all women get tested as often as they should.

On the flip side, even if you have been vaccinated against HPV, you are still recommended to get the Pap test.

Can genital HPV infections be treated?

HPV infections cannot be treated; however, the symptoms of HPV can be treated, at least to some extent. For example, genital warts can be treated with medications or surgically removed; however, they may return, and the patient may still be infected with HPV and could, therefore, still transmit the infection.

The vaccine

How is the HPV vaccine made?

The HPV vaccine is made using a protein that resides on the surface of the virus. The protein is grown in the lab in yeast cells. Once the protein is grown, it assembles itself to look like the HPV virus; however, importantly, it does not contain HPV genetic material, so it can’t reproduce itself or cause illness. The vaccine is composed of the surface protein from nine different types of HPV.

Who should get the HPV vaccine?

The CDC recommended that all adolescents between 11 and 12 years of age receive the HPV vaccine.

The vaccine is given as two shots separated by 6 to 12 months if started before 15 years of age. For those 15 years and older, and teens of any age with a compromised immune system, three doses are recommended. The second shot should be given one to two months after the first, and the third shot, six months after the first. Recently, the HPV vaccine was licensed for use in people up to 45 years of age.

Learn more about why adolescents and teens are recommended to get HPV vaccine by watching this short video, part of the series Talking About Vaccines with Dr. Paul Offit.

Does the HPV vaccine work?

Yes. The HPV vaccine was originally studied in about 30,000 girls and young women between 9 and 26 years of age. Studies determined that the vaccine prevented 9 of 10 HPV infections and was completely effective at preventing persistent infections and Pap smear changes that predict cervical cancer. Subsequent studies showed that HPV vaccine prevented HPV infection, anal and genital warts, and anal cancer in men.

In Australia, where a school-based immunization program was implemented, they have seen dramatic reductions in pre-cancerous cervical changes in young women as well as genital warts in both young men and young women.

Is the HPV vaccine safe?

Yes. Because the HPV vaccine is made using only the surface protein from the virus, it can't cause HPV and, therefore, can't cause cervical cancer. The vaccine may cause redness and tenderness at the site of injection. The vaccine may also cause a low-grade fever in a small number of recipients.

More than 100 million doses of HPV vaccine have been given to people in the United States, and safety networks have continued to monitor reactions to the HPV vaccine since its licensure. Despite concerns raised by the media and some citizen groups, no cause-effect links have been found between HPV vaccine and adverse events, including blood clots, allergic reactions, strokes, seizures, Guillain-Barré Syndrome (GBS, a rare cause of paralysis), birth defects, miscarriages, infertility or premature ovarian failure, or infant/fetal deaths. While fainting episodes following HPV vaccination have been reported, the rates have not been higher than those following receipt of other vaccines for teens. Because of the possibility of fainting, teens are recommended to remain at the office for about 15 minutes after getting immunized.

Other questions you might have

Why do adolescents need the HPV vaccine?

The HPV vaccine is recommended before the start of sexual activity for two reasons:

  • Young people tend to get infected more frequently. In fact, about half of all new infections are diagnosed in girls and young women between 15 and 24 years of age.
  • It takes six months to complete the series, so even though your son or daughter may not be active now, or even in six months, it is better to have the series completed sooner rather than later.

What HPV testing is available?


HPV tests for men are not available, and most HPV infections clear on their own without causing problems. However, health problems caused by HPV, which can include genital warts, anal cancer, penile cancer or cancers of the head and neck, can be checked by visiting your doctor.


Women can get HPV tests and/or Pap tests to determine whether they have an HPV infection that can lead to cancer. Both tests detect early health problems that can lead to cervical cancer, but neither checks for warning signs of other cancers, fertility or other STDs. Although both tests have a common goal, they do have their differences:

Pap test (Pap Smear)

  • Recommended for women 21 and older.
  • Involves scraping the cervix to identify any abnormal changes in cells of the cervix that could later develop into cancer.
  • Results are typically reported as “normal,” “unclear,” or “abnormal”:
    • “Normal” means that no changes were found in the cells
    • “Unclear” indicates that the cells look like they could be abnormal
    • “Abnormal” means that changes in cervical cells were found
  • If your Pap test comes back “normal,” you should still get Pap tests according to the recommended schedule to be sure new changes haven’t occurred.
  • If your Pap test comes back “unclear” or “abnormal,” more testing will be required.

HPV test

  • Most often recommended for women 30 and older and women 21 and older who have had an abnormal Pap test.
  • Typically performed at the same time as a Pap test, using either the same sample as the Pap test or a second sample of cells scraped from the cervix.
  • “Positive” results mean that your cervix has the types of HPV commonly linked to cervical cancer. “Negative” results mean that you do not have any types of HPV that are specifically linked to cervical cancer.
  • Helps your doctor determine how frequently you should be tested and whether other tests should be performed.

If both tests are normal, it is highly unlikely that serious cervical cell changes will develop in the next three years; however, regular wellness visits should not be skipped.

If either test is abnormal, more testing will be completed. Abnormal results do not mean that you have cervical cancer, but that cells in your cervix could eventually become cancerous. However, finding the abnormal cells early allows for more successful treatment.

Do young women who get the HPV vaccine still need to get Pap tests?

Yes. The HPV vaccine prevents the types of HPV that cause about 9 of every 10 cervical cancers. Because the vaccine doesn't prevent all types of HPV that cause cancer, women still need to get routine Pap tests.

Do people who have received the HPV vaccine still need to worry about sexually transmitted diseases?

Yes. The HPV vaccine doesn't prevent other sexually transmitted diseases such as syphilis, gonorrhea, chlamydia and herpes virus, and the HPV vaccine doesn't prevent all of the dangerous types of HPV; it prevents most of them. Vaccinated individuals should still practice safe sexual behaviors (monogamy or limiting the number of sexual partners, and condom use).

Should males get the HPV vaccine?

Yes. Males are recommended to get the HPV vaccine for two reasons:

  • To protect themselves from anal and genital warts as well as cancers of the head, neck, anus, and penis.
  • To reduce transmission of the virus to sexual partners

Can the HPV vaccine treat cervical cancer?

No. Unfortunately, therapeutic trials of HPV vaccine have shown that the vaccine doesn't cause a regression in Pap smear changes that precede cervical cancer.

Relative risks and benefits

The HPV vaccine protects against certain cancers and genital warts, and it is safe. The only known side effects are mild, such as pain, redness or swelling at the injection site or low-grade fever. Therefore, the benefits of the HPV vaccine outweigh its risks.


Adolescents and teens; adults up to 45 years old who want to protect themselves

Disease risks

  • Cervical cancer
  • Genital warts
  • Cancers of the head and neck
  • Cancers of the anus and penis
  • Can be fatal

Vaccine risks

  • Pain, redness and tenderness at the injection site
  • Low-grade fever
  • Allergic reaction (1 in 1 million recipients)


Plotkin SA, Orenstein W, Offit PA, and Edwards KM. Human papillomavirus vaccines in Vaccines, 7th Edition. 2017, 430-455.

Reviewed by Paul A. Offit, MD on November 14, 2018

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.