HPV: What you need to know

Human papillomavirus (HPV) is a virus that is spread through intimate skin-to-skin contact. There are more than 200 strains of HPV. Some types can cause warts on the hands, feet, or face. Other strains can infect the skin in the genital area, including the vulva, vagina, cervix, penis, scrotum, rectum, or anus.

Some strains of HPV can cause changes in the cells that line the cervix, and these changes sometimes lead to cervical cancer. Fourteen strains of HPV are related to cancer risk, but two types (16 and 18) are the most common, accounting for about 70 percent of all invasive cervical cancers. HPV can also lead to cancer of the head and neck, anus, vulva, and penis.

Some types of HPV will cause warts on the skin, but most infected people will experience no symptoms. Because it is possible to have HPV and not know it, an infected person can unknowingly spread HPV to another person.

HPV is very common. About 80 percent of unvaccinated individuals will be infected with HPV at some point during their lives. The Centers for Disease Control and Prevention (CDC) estimates that approximately 42 million Americans are currently infected with types of HPV that are known to cause disease, and about 13 million new infections occur every year. 

In most cases, it is not diagnosed. Most people will never know if they have been infected with HPV. Some cases of HPV are diagnosed due to visible genital warts. It is also possible to have a positive HPV test as part of cervical screening. This test detects the types of HPV that put people at highest risk for disease, but it does not screen for every strain of HPV.

Unfortunately, there is no treatment for HPV infection. In most cases, the body’s immune system will fight the virus and clear the infection, but that can take up to two years. And many times, the infection persists, putting that individual at risk for serious complications, including cancer.

When the immune system fails to clear an HPV infection — which happens about 10 percent of the time — HPV infections persist, usually without symptoms. These persistent infections may lead to cellular changes that can develop into cancer, often after as long as 15 to 20 years. Regular cervical screenings, like Pap smears, can detect precancerous cells before they turn into cancer.

The HPV vaccine, known as Gardasil 9, protects against nine strains of HPV that cause cancer in people. For individuals younger than 15, the vaccine is given in two doses, separated by six to 12 months. Patients 15 or older receive three doses.

The Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recommend that all adolescents between 9 and 12 years of age receive the HPV vaccine. The CDC also recommends vaccination for everyone through age 26, if they were not adequately vaccinated when they were younger. 

Adults aged 27–45 should discuss HPV vaccination with their primary care providers (PCPs). A PCP might recommend vaccination for some patients in this age group, but vaccination generally provides less benefit for older patients, because most will already have been exposed to the virus. The HPV vaccine is not approved for use in people older than 45.

• For patients younger than 15, the vaccine is given in two doses separated by 6 to 12 months.
• For patients 15 years and older, or younger individuals with a compromised immune system, the vaccine is given in three doses. The second shot is given one to two months after the first. The third shot should be given six months after the first. 

Vaccination against HPV is much more effective if it is completed before an individual is exposed to the virus for the first time. In addition, research has shown that the vaccine produces better immunity to fight infection when it is given at younger ages, compared with older ages.

HPV vaccination also protects boys against HPV-related cancers. The CDC estimates that HPV causes about 16,000 cases of cancer in males every year — that’s almost three out of every four HPV-related cancers. Vaccination also prevents the spread of the virus. 

Yes. The earliest studies of the vaccine, in girls and young women aged 9–26 years, concluded that  the vaccine prevented up to 90 percent of cancers caused by HPV infection. A more recent Scottish study detected no cases of cervical cancer in women born from 1988–1996 who were fully vaccinated against HPV between the ages of 12 and 13. The vaccine has also been shown to reduce the incidence of genital warts and pre-cancerous changes to cervical cells. 

Yes, the HPV vaccine has been shown to be very safe. Before FDA approval, clinical trials tested the vaccine in more than 28,000 male and female participants. Since the first HPV vaccine was approved in 2006, more than 120 million doses have been distributed in the US, while the vaccine has been continually monitored for safety.

In all these years of safety monitoring, no serious safety concerns have been identified, other than the possibility of fainting after vaccination — something that commonly happens to adolescents after any vaccination. Like other vaccines, the HPV vaccine may cause redness and tenderness at the site of the injection. A small number of individuals may also experience a low-grade fever after vaccination.

The vaccine uses only the surface protein from the virus, so it can’t cause HPV or HPV-related cancers. No causal links have been found between the HPV vaccine and adverse events, including blood clots, allergic reactions, strokes, seizures, Guillain-Barré syndrome (a rare cause of paralysis), birth defects, miscarriages, or infertility.