Human papillomavirus (HPV) is a virus that causes cervical cancer and genital warts. Over time, infection with certain types of HPV can lead to cancer of the cervix, which affects more than 13,000 American females every year. HPV can also cause cancers of the vulva and vagina in females, although these cancers are much less common than cervical cancer. HPV also causes cancers of the penis in males and of the anus and oropharynx (mouth and throat) in both males and females.
Six vaccines (brand names: Gardasil, Gardasil-9, Cervarix, Cervavac, Walrinvax, Cecolin) are globally available to prevent infection with types of HPV known to cause cervical cancer. These vaccines are safe, and they significantly reduce the number of females who develop cervical abnormalities (“pre-cancer”) that can lead to cancer. Studies have also documented that HPV vaccination reduces rates of cervical cancer. Gardasil, Gardasil-9, and Cervavac also prevent infection with the two HPV types that cause 90 percent of genital warts.
This article discusses HPV infection and the HPV vaccine. Cervical cancer, cervical cancer screening, and genital warts are discussed in more detail separately (see “Patient education: Cervical cancer treatment; early-stage cancer (Beyond the Basics)” and “Patient education: Cervical cancer screening (Beyond the Basics)” and “Patient education: Genital warts in women (Beyond the Basics)”). An article that discusses vaccines recommended for adults is also available. (See “Patient education: Vaccines for adults (Beyond the Basics)”.)
WHAT IS HPV?
Human papillomavirus (HPV) is a virus that is spread by skin-to-skin contact, including sexual contact. This includes sexual intercourse (vaginal sex), oral sex, anal sex, or any other contact involving the genital area (eg, hand to genital contact). While condoms are an important way to prevent most sexually transmitted infections, they do not provide complete protection from HPV infection, because they do not cover all exposed genital skin.
The risk of HPV exposure increases with the number of sexual partners you have. Having sex with a partner who has had many other partners in the past also increases your risk. It has been estimated that 75 to 80 percent of sexually active adults will acquire at least one genital HPV infection before the age of 50. A majority of individuals become infected for the first time with one or more HPV types in the anogenital region between ages 15 and 25 years.
Most people who are infected with HPV have no signs or symptoms, and in most cases never develop any problems caused by HPV. In 10 to 20 percent of females, however, HPV infection does not go away. In this situation, there is a greater chance of developing cervical pre-cancer and then cancer. It usually takes, on average, 20 to 25 years for a new HPV infection to cause cervical cancer. For this reason, it’s important to get regular screening (Pap or HPV tests, or both) to detect any cervical abnormalities early, before cancer develops. (See “Patient education: Cervical cancer screening (Beyond the Basics)”.)
Over 100 different types of HPV have been identified; more than 40 of these are known to infect the cervix, and approximately 15 are known to cause cervical cancer. Researchers have labeled the HPV types as being high or low risk for causing cervical cancer.
●HPV types 6 and 11 cause about 90 percent of genital warts. These types are considered low risk because they do not cause cervical cancer. (See “Patient education: Genital warts in women (Beyond the Basics)”.)
●Types 16 and 18 are the high-risk types that cause most (about 70 percent) cases of cervical cancer. HPV types 31, 33, 45, 52, and 58 are also high-risk types, causing about 20 percent of cervical cancers. Other high-risk types (35, 39, 51, 56, and 59) can also cause cervical cancers but are less common.
Six HPV vaccines are available globally. The three vaccines protect against the following types of HPV:
●Gardasil-9 helps to prevent infection with nine HPV types (6, 11, 16, 18, 31, 33, 45, 52, and 58).
●Gardasil and Cervavac help to prevent infection with four HPV types (6, 11, 16, and 18).
●Cervarix, Walrinvax, and Cecolin help to prevent infection with HPV types 16 and 18.
●In the United States, only Gardasil-9 is available.
HPV VACCINE TIMING AND DOSE
All of the HPV vaccines are given by injection. The recommended timing and schedule are the same for both males and females. Dosing depends on your age and how healthy your immune system is. Vaccine schedules also differ depending on the country in which you live. In the United States:
●If you are younger than 15 years old with normal immune function, you should get two injections at least six months apart.
●If you are 15 years of age or older with normal immune function, you should get three injections. The second dose is given one to two months after the first, and the third dose is given six months after the first.
●If you have HIV infection or are immunocompromised (eg, have another health condition that weakens your immune system), you should get three injections regardless of the age at which you start the vaccination series.
It is best to try to get all the recommended doses. If you miss a dose, talk to your health care provider about how many more doses you need.
Who should be vaccinated? — In the United States, routine HPV vaccination is recommended for all children ages 11 to 12 years and can be given as early as 9 years of age. “Catch-up” vaccination is recommended for all people up to 26 years of age who have not yet received it. The HPV vaccine is also approved by the US Food and Drug Administration (FDA) for individuals aged 27 to 45 years; the decision to vaccinate adults in this age group should be individualized, typically in conversation with a health care provider, as some people in this age group may still benefit from it.
With any HPV vaccine, you will have the greatest protection from HPV if you are vaccinated before becoming sexually active. The vaccine does not help to get rid of HPV infection or any cervical abnormality after it has occurred. However, if you are under 26 years old and you have been sexually active, had genital warts, a positive HPV test, or an abnormal Pap test, you may still obtain some (although smaller) benefit from the HPV vaccine since the vaccine will still cover HPV types that you were not previously exposed to.
It is important to keep in mind that the vaccine works best if given before sexual activity begins (even many years before). Sometimes, parents or caregivers are hesitant to get their children vaccinated. Some people worry that it will lead to children becoming sexually active earlier than they otherwise would. However, there is no evidence that this happens.
Some also worry that the vaccine may have serious side effects, but studies have clearly shown that the available HPV vaccines are very safe.
How long am I protected? — While experts do not know exactly how long the vaccine protects against HPV infection, there has been no evidence to suggest that the HPV vaccine loses any ability to provide protection over time.
Do I still need cervical cancer screening? — Females do not need to have a pelvic exam or test for cervical cancer (eg, Pap and/or HPV test) before getting the HPV vaccine. In the United States, regular cervical cancer screening is generally recommended beginning at age 21.
However, getting the HPV vaccine does not mean that you can skip cervical cancer screening in the future, since the vaccine does not eliminate infections acquired prior to vaccination. In addition, other types of high-risk HPV, which are not prevented by the vaccine, can also cause cervical cancer. (See “Patient education: Cervical cancer screening (Beyond the Basics)”.)
Anal cancer screening tests may be available for individuals known to be at increased risk of anal cancer, but these are not yet done everywhere.
There are also no approved screening tests for oropharyngeal (mouth and throat) cancer, but a thorough dental examination may reveal signs of oropharyngeal cancer or pre-cancer.
HPV VACCINE SIDE EFFECTS AND PRECAUTIONS
The HPV vaccine may cause mild redness, tenderness, or swelling near the injection site. There is no thimerosal (a mercury derivative used as a preservative) in the HPV vaccine. There may be an increased risk of passing out after an injection of HPV vaccine, so it is a good idea not to stand up too soon after getting the vaccine.
The vaccine is not currently recommended during pregnancy, although there are no known risks to a fetus if the vaccine is given.
If you are concerned about the safety of the vaccine or possible side effects, your health care provider can talk to you about this in more detail.
HOW EFFECTIVE IS THE VACCINE?
Studies have shown that:
●HPV vaccination in females is very effective in preventing HPV infections and cervical pre-cancers and cancers caused by HPV types targeted by the vaccine.
●HPV vaccination in females reduces the risk of genital warts and of transmitting the warts to their sexual partners.
●HPV vaccination in males reduces the risk of developing genital warts and penile HPV infection, which decreases the risk of HPV transmission to sexual partners.
●HPV vaccination also reduces the risk of anal cancer in both males and females.
●HPV vaccination prevents oral HPV infection, which is associated with oropharyngeal (mouth and throat) cancer. It is expected that the vaccine can reduce the risk of this cancer as well, and the vaccine is US Food and Drug Administration (FDA) approved for this indication.