Vaccines are medicines that boost the immune system's natural ability to protect the body against "foreign invaders," mainly infectious agents that may cause disease. When an infectious microbe invades the body, the immune system recognizes it as foreign, destroys it, and "remembers" it to prevent another infection should the microbe invade the body again in the future. Vaccines take advantage of this defensive memory response. Most vaccines are made with harmless versions of microbes killed or weakened microbes, or parts of microbes that do not cause disease but are able to stimulate an immune response against the microbes. When the immune system encounters these substances through vaccination, it responds to them, eliminates them from the body, and develops a memory of them.
Human papillomaviruses (HPVs) are a group of more than 200 related viruses. More than 40 HPV types can be easily spread through direct sexual contact, from the skin and mucous membranes of infected people to the skin and mucous membranes of their partners. They can be spread by vaginal, anal, and oral sex. HPVs cause several types of cancer.
- Cervical cancer: Virtually all cases of cervical cancer are caused by HPV, and just two HPV types, 16 and 18, are responsible for about 70 percent of all cases.
- Anal cancer: About 95 percent of anal cancers are caused by HPV. Most of these are caused by HPV type 16.
- Oropharyngeal cancers (cancers of the middle part of the throat, including thesoft palate, the base of the tongue, and the tonsils): About 70 percent of oropharyngeal cancers are caused by HPV. In the United States, more than half of cancers diagnosed in the oropharynx are linked to HPV type 16.
- Rarer cancers: HPV causes about 65 percent of vaginal cancers, 50 percent of vulvar cancers, and 35 percent of penile cancers. Most of these are caused by HPV type 16.
High-risk HPV types (Type 16, 18) cause approximately 5 percent of all cancers worldwide. People who are not sexually active almost
never develop genital HPV infections. In addition, HPV vaccination before sexual activity can reduce the risk of infection by the HPV
types targeted by the vaccine.
The Food and Drug Administration (FDA) has approved Gardasil, and Cervarix vaccines to prevent HPV infection. These vaccines provide strong protection against new HPV infections, but they are not effective at treating established HPV infections or disease caused by HPV. The World Health Organization (WHO) recommends HPV vaccines as part of routine vaccinations in countries that can afford them, along with other prevention measures. The vaccines require two or three doses depending on how old the person is. Vaccinating girls around the ages of nine to thirteen is typically recommended. The vaccines provide protection for at least eight years. Cervical cancer screening is still required following vaccination. Vaccinating a large portion of the population may also benefit the unvaccinated. In those already infected the vaccines do not help. HPV vaccines are approved for males in several countries, including Canada, Australia, South Korea, the United Kingdom, and the United States.