There are two HPV vaccines available in Canada: Cervarix and Gardasil. Both are highly protective against new infections with virus types 16 and 18 and therefore significantly reduce the risk for cervical cancer. In addition, Gardasil also contains virus types 6 and 11, which are the primary causes of genital warts. It’s important to recognize that these vaccines only protect against new infections and will not alter risk after a patient has been infected with a given virus type. Given that the majority of these infections are sexually transmitted and that the risk increases with the number of partners, the greatest benefit will be observed when administered to individuals prior to the onset of sexual activity.

Both vaccines are indicated for immunization of young girls (i.e. age 9 and older) and women; because of greatest cost benefit, younger girls have been targeted for universal programs. However, significant benefit is expected in older age groups with the relative benefit decreasing as the number of exposures to wild type virus increases. There’s no risk (and benefit may still be expected) from vaccinating women who have had extensive exposure risk. However, the reduced benefit may not justify the vaccine cost to the patient. Generally speaking, I’d recommend immunization of all girls and young women (a commonly used cut-off is 26 years) and offer it to other older women who have ongoing risk for new infection.

As for males, immunization of all boys and young men with Gardasil is recommended as of last month, but it remains to be seen whether universal funding will become available in Canadian provinces.

The primary rationale for immunizing boys has been to reduce HPV transmission among women, and its associated oncogenicity. But research is also pointing to long-term health benefits in men. It’s now recognized that about a quarter of mouth cancers and a third of throat cancers are HPV-associated, and men suffer far higher rates of these cancers than women.1 There’s also now direct evidence that quadrivalent HPV vaccine can reduce incidence of anal cancers.2

References

1. Ryerson AB et al, Cancer 2008;113(10 Suppl):2901-9.
2. Palefsky JM et al, NEJM 2011;365:1576-85.