About 70 to 80 per cent of the population gets a human papillomavirus (HPV) infection at some point in their life. Most of the time, a person’s body reacts to the virus and fights it off without even showing symptoms. However in some cases, HPV can develop into cervical cancer.
The good thing about cervical cancer caused by HPV is that it is takes a long time to occur, making it possible to prevent it with regular screening using the Pap test.
“Cervix cancer has a long precancerous stage where on average it takes 10 years between getting a cancer-causing strain of HPV and actually developing cancer,” explains Dr. Amanda Selk, staff gynecologist at Women’s College Hospital. “That is why it is so important to get screened. If your doctor finds precancerous cells or changes, they can treat the virus before it becomes cancerous.”
HPV and Paps
The HPV strains that are linked to cervical cancer are part of one of the most common families of viruses in the world today. These strains are transferred between partners through genital skin-to-skin contact and can result in genital warts, precancerous lesions and cancer.
HPV is extremely contagious, and is not necessarily transmitted through intercourse. Any skin-to-skin genital contact can pass the virus. For that reason, condoms may decrease the risk of transmission, but cannot prevent it.
Those at higher risk for consequences of HPV infection include individuals with HIV, organ transplants or lupus patients who are on immunosuppressing drugs because their bodies don’t fight the virus as well as healthy people. Smoking can make HPV worse, so smokers who already have the virus are at an increased risk of persistent or long-term infection which increases cancer risk.
Protection begins with the Pap
For optimal protection from cervical cancer, regular screening is necessary, especially since most women show no signs of the virus. The tool used for screening is a Pap test, often referred to as a Pap smear. The test identifies precancerous cells and changes that may indicate the development of cervix cancer.
“Over the last 60 years, cervix cancer rates have decreased by 70 to 80 per cent in Canada due to the use of the Pap,” says Dr. Selk. It is important to remember that a Pap does not test for HPV, but only the precancerous changes caused by HPV that may indicate a need for additional tests and treatment. An HPV test is a separate test which is currently used in certain cases of abnormal Paps but will likely replace Paps as the main form of screening in the future.
During your Pap test, the doctor will examine your cervix and take samples.
Cancer Care Ontario’s cervical cancer screening guidelines advise that women in Ontario who are, or have ever been, sexually active should have a Pap test every three years from age 21 through 70. After age 70, women who have had three normal Pap tests in the preceding 10 years can stop screening.
HPV vaccination began around 2004 after a rigorous clinical trial process. The goal of the vaccination is to create a resistance before infection occurs. That’s why ideal candidates for the vaccines are young girls between the ages of nine and 13 before they have any sexual contact. Each province has a different vaccination program where the vaccine is covered. You can also opt to pay for the vaccine yourself or see if it’s covered by your private health insurance if you have any. In some provinces boys can also receive the vaccine free of charge.
Even though there are over 200 strains of HPV, the vaccines typically only cover two or four of these strains. These include strains #6 and #11, which cause 90 per cent of genital warts, and strains #16 and #18, which contribute to 70 per cent of cervix cancers.
“Despite being older, you may still receive some benefit from the vaccine,” explains Dr. Selk. “Even if you have had HPV previously, you may not have had all the strains the vaccines cover and the vaccine may still help prevent transmission. Studies have even shown benefit in women who’ve had treatment for HPV in the past.”
There are two main vaccines available and approved for use in Canada, however some provinces’ vaccination programs may not cover both.
- protects against four strains of HPV (#6, #11, #16, and #18)
- coverage consists of three shots
- approved for girls and women ages 9-45, and boys and men ages 9-26, however boys and men are only covered in some provinces
- protects against two strains of HPV (#16 and #18)
- coverage consists of three shots
- approved for girls and women ages 10-25
Vaccination consists of three shots. If you miss a shot you might not have full coverage against the targeted strains, although there is some data that two shots may be effective and the number of shots needed may decrease in the future.
This information is provided by Women’s College Hospital and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: Oct. 28, 2014