Human Papillomavirus (HPV) Vaccine

The HPV vaccine, brand name Gardasil 9, protects against infection with human papillomaviruses (HPV). HPV is a group of more than 200 related viruses, of which more than 40 are spread through direct sexual contact. Among these, two HPV types cause most genital warts, and about a dozen HPV types can cause certain types of cancer—cervical, anal, oropharyngeal, penile, vulvar, and vaginal (1).

Gardasil 9 (2), the HPV vaccine used in the U.S., prevents infection with the following nine types:
•    HPV types 6 and 11, which cause 90% of genital warts 
•    HPV types 16 and 18, two high-risk types that cause about 70% of cervical cancers and an even higher percentage of some of the other HPV-caused cancers 
•    HPV types 31, 33, 45, 52, and 58, high-risk HPVs that account for an additional 10% to 20% of cervical cancers

The Centers for Disease Control and Prevention (CDC) establishes recommendations regarding all vaccination in the United States, including HPV vaccination. CDC recommends the HPV vaccine for (3):

• Children and adults ages 9 through 26 years. HPV vaccination is routinely recommended at age 11 or 12 years; vaccination can be started at age 9. HPV vaccination is recommended for all persons through age 26 for those who were not adequately vaccinated earlier. 
• Adults ages 27 through 45. Although the HPV vaccine is approved by the U.S. Food and Drug Administration (FDA) to be given through age 45, HPV vaccination is not recommended for routine administration to adults ages 27 through 45. Instead, clinicians can consider discussing with patients in this age group who were not adequately vaccinated earlier whether HPV vaccination is right for them. HPV vaccination in this age range provides less benefit because more people have already been exposed to the virus. 
• Pregnant women. HPV vaccination should be delayed until after pregnancy, but pregnancy testing is not required before vaccination. There is no evidence that HPV vaccination will affect a pregnancy or harm a fetus.

In the U.S., the HPV vaccine was licensed for two doses in younger recipients and three doses in older recipients.

Researchers have reported evidence that one dose results in protection from infection with the HPV types in the vaccine that is not inferior to the protection obtained through two doses (4).

Clinical trials have shown that the HPV vaccines are highly effective in preventing HPV infections at multiple anatomic sites in both men and women. The protection is maximized when given before first exposure to the virus—that is, before individuals begin to engage in sexual activity, although adults do still receive benefit. In addition to protection against HPV infection and precancer, real-world data have now shown that the vaccine greatly reduces the incidence of cancer (5).

To date, vaccine protection against infections with the targeted HPV types has been found to last for more than a decade.

Like other immunizations that guard against viral infection, the HPV vaccine stimulates the body to produce antibodies that, in future encounters with HPV, bind to the virus and prevent it from infecting cells. In other words, the vaccine-induced antibodies prevent HPV infections.

The current HPV vaccine is based on virus-like particles (VLPs) that are formed by HPV surface components. VLPs are not infectious because they lack the virus’ DNA. However, they closely resemble the outer surface of the natural virus. The VLPs have been found to be strongly immunogenic, which means that they induce high levels of antibody production by the body. This makes the vaccine highly effective.

The vaccine does not prevent other sexually transmitted diseases, nor treat existing HPV infections or HPV-caused disease.

The combination of HPV vaccination and cervical screening can provide the greatest protection against cervical cancer. Also, HPV vaccination reduces the prevalence of HPV at sites other than the cervix for which there is no population screening methods.

Not only does vaccination protect vaccinated individuals against infection by the HPV types targeted by the vaccine but vaccination can also reduce the prevalence of the vaccine-targeted HPV types in the population, thereby reducing infection in individuals who are not vaccinated (a phenomenon called herd protection). For example, in U.S., as female vaccination rates increased, prevalence of oral HPV infections in males decreased, indicating herd immunity (6).

Widespread HPV vaccination has the potential to reduce cervical cancer incidence around the world by as much as 90%. In addition, the vaccines may reduce the need for screening and subsequent medical care, biopsies, and invasive procedures associated with follow-up from abnormal cervical screening, thus helping to reduce health care costs and anxieties related to follow-up procedures. Already, the incidence of cervical cancer has declined in the United States.

HPV vaccination is also very important to prevent other HPV-associated caners such as oropharyngeal, vulvar, and anal cancers, whose incidence have been increasing. There are no formal screening programs for the general population for the non-cervical cancers, so universal HPV vaccination could have a large public health impact.

Yes. More than two decades of safety monitoring show that the vaccines have caused no serious side effects (7). The most common problems have been brief soreness and other local symptoms at the injection site. These problems are similar to those commonly experienced with other vaccines.

The CDC oversees vaccine safety. Learn more about vaccine safety.

Women who have an HPV infection and/or an abnormal Pap test result that may indicate an HPV infection should still receive the HPV vaccine if they are in the appropriate age group (9 through 26 years) because the vaccine may protect them against high-risk HPV types that they have not yet acquired. However, they should be told that the vaccination will not cure them of current HPV infections or treat the abnormal results of their Pap test (8).

Although the HPV vaccine has been found to be safe when given to people are already infected with HPV, the vaccine provides maximum benefit if a person receives it before he or she is sexually active.

It is likely that someone previously infected with HPV will still get some residual benefit from vaccination, even if he or she has already been infected with one or more of the HPV types included in the vaccine.

Yes. Because the HPV vaccine does not protect against all HPV types that can cause cancer, women who have been HPV vaccinated are advised to follow the same screening recommendations as unvaccinated women. There could be future changes in screening recommendations for vaccinated women.

Most private insurance plans cover HPV vaccination. The federal Affordable Care Act requires most private insurance plans to cover recommended preventive services (including HPV vaccination) with no copay or deductible.

Medicaid covers HPV vaccination in accordance with CDC recommendations, and immunizations are a mandatory service under Medicaid for eligible individuals under age 21. In addition, the federal Vaccines for Children Program provides immunization services for children younger than 19 years who are Medicaid eligible, uninsured, underinsured, or Native American or Alaska Native.

Merck, the manufacturer of Gardasil 9, offers the Merck Vaccine Patient Assistance Program, which provides Gardasil 9 for free to people aged 19 to 45 years who live in the United States, do not have health insurance, and have an annual household income less than a certain amount.

Researchers are working to develop therapeutic HPV vaccines, which instead of preventing HPV infection would prevent cancer from developing among women previously infected with HPV (9-10). These vaccines work by stimulating the immune system to specifically target and kill infected cells. Ongoing clinical trials are testing the safety and efficacy of therapeutic vaccines to treat HPV-related cervical and vulvar lesions.