To coincide with HPV Awareness Month in August, ICRF board member and former Executive Director, Dr. Mark Israel, a pedicatric oncologist responds to questions about HPV and the vaccine.

What is HPV?

HPV is a widely used abbreviation for a large family of viruses, the Human Papilloma Viruses. Selected types (species) of HPV can cause cancer which has led to research and public health efforts to prevent such cancers by preventing the spread of HPV. HPV infection may occur as the result of sexual contact and prevention focuses on encouraging safe sex, early detection and treatment of pre-cancerous disease, and vaccination against viral infection. HPV is the most common sexually transmitted virus in the world.

Can you tell us about the relationship between HPV and cancer? (Do all HPV strains cause cancer?)

HPV infects a limited number of different tissues within the body. These include the skin and the mucosal surfaces, the lining of “internal” surfaces that are in contact with the environment, like the surfaces within the mouth, lungs, or genital organs. Infection spreads by contact between infected tissue and uninfected surfaces of another person.

Infection means that the virus resides within cells of the body. HPV infections are rarely noteworthy because the immune system almost always eliminates infected cells in the months and years following infection. When there is a noticeable consequence of HPV infection, it is as genital warts that appear as bumps, sometimes in clusters, on the genitals or skin around the anus. There are approximately 175 different types of HPV, and approximately 40 of these types have been found in human warts. Genital warts often resolve spontaneously or can be treated by several different approaches. Rarely the virus remains dormant for years, even decades, in these tissues.

About ten types of HPV that can cause warts have been found to cause human cancer, although HPV types 16 and 18 are responsible for the great majority of these cancers.  Cancer arises when HPV genes force the cells they have infected to start replicating by inhibiting naturally occurring “brakes” on cells. Eventually these dividing cells acquire additional mutations that enable them to invade adjacent normal tissue. What “activates” HPV to end dormancy and contribute to the development of cancer is not known.

What kinds of cancer are caused by HPV?

It is estimated that approximately 15 percent of all cancers are the result of infection with the seven known cancer-causing viruses. Amongst the cancers caused by viral infection, the most common is cervical cancer. As many as 12,000 cases of cervical cancer are diagnosed each year in the U.S. and 80 percent of these are thought to be the result of infection by either HPV16 or HPV18. Cervical cancer is the second leading cause of cancer mortality in women worldwide, causing 240,000 deaths annually. The other types of cancer caused HPV infection are anal cancer, cancer of the mouth or throat, cancer of the genitals, and cancer of the anus.

How do I know if I have HPV? How is it treated?

If cells that are thought to be infected with HPV can be obtained, common laboratory tests can determine if the virus is present. Usually, such cells are obtained by scraping the skin or performing a biopsy. Genital warts caused by HPV are removed by a number of types of procedures such as freezing the infected tissue or surgically removing it. Pre-cancerous or cancerous tissues containing HPV are treated with various combinations of a variety of modalities including surgery, radiation, and chemotherapy.

A related and widely known common test is the Pap smear. Pap smears contain cells removed from the cervix and examined by a pathologist for the changes in cells that occur as the result of HPV infection (or any other cause of these “pre-cancerous” changes). A test for HPV can be done on the same specimen used for a Pap smear. Pap smears have led to a dramatic decrease, up to 70 percent, in the incidence of cervical cancer in countries where such expensive testing is available. If a Pap smear is found to contain pre-cancerous cells, the region of cervix from which it was taken can removed.

What are cancer vaccines? Is the HPV vaccine safe? Effective? Why is it administered at a young age?

Vaccines are substances that can stimulate the body’s immune system to fight off a disease or the agent that can cause a disease, for example a virus. There are many ways in which vaccines can be used to prevent or treat disease. Three HPV vaccines available in the U.S. are approved for the prevention of cervical cancer and other conditions caused by certain types of HPV. HPV vaccines program the body’s immune system to be highly effective in eliminating types of HPV that cause cancer.  

It is important to be vaccinated because 85 percent of adults will get HPV infections during their lifetime and the current vaccines are almost 100 percent effective in protecting individuals from HPV-caused disease if administered in the recommended manner. The CDC has reported that the HPV infections with types of HPV that cause most of the HPV-related cancers have dropped 86 percent among teenage girls following the introduction of vaccines. Among vaccinated women, the percentage of cervical pre-cancers caused by the HPV types most often linked to cervical cancer has dropped by 40 percent. Side effects of HPV vaccines have been monitored for more than a decade and have been found to be rare, and more important, mild, and short lived. These side effects are like those that occur with other vaccines including pain at the injection site, fever, and headache.

HPV vaccination is recommended for everyone through age 26 years. In addition to those vaccines given in early childhood, vaccination is recommended at 11-12 years of age for meningococcal disease (meningitis), COVID-19, and HPV.  Most children only need two doses of the HPV vaccine when vaccinated before age 15 years of age. It is important to be vaccinated as a preteen because vaccine efficacy is greatest if the vaccine is administered before onset of sexual activity and protective responses to the vaccine are highest when the vaccine is administered between 9 and15 years of age.