Human Papilloma Virus (HPV) is the virus that causes more than 90% of cervical cancers, roughly 70% of vulvar and vaginal cancers, most anal cancers, and more than 60% of penile cancers. While oropharyngeal cancers (those affecting the mouth, throat and neck) have traditionally been caused by tobacco and alcohol, the CDC reports that 70% of cancers of the oropharynx may be linked to HPV.
Prevalence of HPV Infection in Adults
Eighty-five percent of adults will have had HPV at some point in their lives. The highest incidence of new HPV infections has been seen in women under 20 years of age. People commonly think that older adults or people in monogamous relationships are not at risk of acquiring HPV infections and HPV-related disease such as genital warts, and cancers. While the risk of HPV is higher in the teenage years and in the early 20s, research shows that risk is not limited to young people or those who are dating, and HPV infections continue to increase as patients get older.
For women over the age of 30, if they do not have an HPV infection, their risk of acquiring HPV over five years is more than 20%. For women over the age of 45, the 5-year risk of acquiring HPV is still more than 10%. The risk is not zero, regardless of age.
A study from the National Health and Nutrition Examination Survey 2007-2010 (including American women ages 18-59 years) showed that the prevalence or chance any of those women had an HPV infection was 42% across the group, and as high as 59% in non-Hispanic black women. While the prevalence of HPV in women declines with age, the prevalence of HPV in adult women over 50 is still quite high, at 35%.
The prevalence of HPV is even higher in men, about 63%, and studies show it does not decline with age.
In Ontario, we immunize girls and boys in grade 7 against HPV because the immune response to the vaccine is highest from age 9-15, and we hope to protect them before they become sexually active. There is still a need to immunize adults: sexual behaviour patterns are changing with high rates of online dating, divorce, and infidelity, so risk of exposure may persist or recur. But new exposure is not the only reason to vaccinate...
Clearance Rates of HPV
Persistence of HPV infections increases with age, so if you do acquire HPV, the chance you will be able to clear it decreases the older you get. And the forms of HPV most linked to cancer (such as type 16 and 18) are more aggressive and harder to clear.
Some patients may have latent (inactive) HPV infections that only surface as they get older; this may explain why some women in monogamous relationships or who are no longer sexually active develop HPV-related disease: they had an earlier exposure to HPV, but only as they age does this infection become active and cause illness.
What About Natural Immunity from Previous Infection?
Many women (and men) do not develop any natural antibodies to HPV infection, and infection with one strain of HPV does not appear to protect us from infection with other types of HPV. Even if you do develop antibodies, these natural antibodies do not seem to protect against subsequent infection, even with the same type of HPV! HPV antibodies from a natural infection basically only tell us that you have had an exposure - they do not protect you from future HPV infection.
Universal Vaccination: Regardless of Age
The wonderful news is that HPV immunization produces high levels of antibodies that are protective against subsequent infection. The antibodies produced from vaccination are long-lasting and do not require booster dosing once you have completed the full series of HPV vaccines. HPV vaccination reduces recurrence of disease in those who have previously been exposed and treated for disease, and has reduced recurrence of disease in the cervix, vulva, and anal precancerous cells, and for external genital warts.
The Society of Gyn-Oncologists of Canada (GOC) recommend universal HPV vaccination, regardless of age. The National Advisory Committee on Immunization (NACI) recommends vaccination in all individuals, female and male, from age 9, with no upper age limit.
It is never too late to be immunized against HPV. It's a vaccine that PREVENTS CANCER.
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