HPV vaccines prevent infection from high-risk HPV types associated with about 70 per cent of cervical cancers. About 30 per cent of cervical cancers will not be prevented by the vaccines. While hetting vaccinated against HPV is a complimentary practice, it is not a replacement for cervical cancer screening with Pap and HPV tests. In addition, the length of time that HPV vaccines last is not full known. Data collected suggests that protection lasts up to five years with Gardasil and up to 6.4 with Cervarix in cases where women were not infected with HPV at the time of vaccination. More information is needed to answer questions about its long-term effectiveness and whether booster doses will be needed for continued protection [27].
A 2012 US study on the HPV vaccine and immunization showed that in post-vaccination prevalence rates, a significant decrease in HPV infection occurred in the community setting, while also providing herd immunity. Herd immunity describes a decrease in infection rates among unimmunized individuals when a critical mass of people in a community are mmunized against a contagious disease [28].
In comparing pre- and post-vaccination HPV prevalence rates, the researchers found that the prevalence of vaccine-type HPV decreased by 58 per cent overall, from 31.7 per cent to 13.4 per cent. The decrease was highest among vaccinated participants (69 per cent), but also was substantial amongst those who were unvaccinated (49 per cent) [29].
HPV Vaccinations in Canada
There are now three HPV vaccines authorized for use in Canada: Gardasil, Cervarix, and Gardasil 9. All three protect against infections from the high-risk types of HPV, HPV-16 and HPV-18. As well as being responsible seventy per cent of all cervical cancers, these types of HPV are also linked to cancer of the anus, vulva, vagina and penis, as well as some oraland oropharyngeal cancers.
Gardasil protects against HPV-6 and HPV-11, which are responsible for ninety per cent of genital warts. Gardasil 9 also protects against 6 and 11, as well as five other types of HPV that can cause cancer.
Gardasil
Gardasil is a quadrivalent vaccine, protecting against four different types of HPV: -6, -11, -16 and -18. It protects females between the ages of 9 to 45 against precancerous conditions of the cervix, vagina and vulva. In females and males between 9 and 26 years of age, Gardasil helps prevent precancerous conditions of the anus or anal cancer. Gardasil also protects males between 9 and 26 and females between 9 and 45 against anogenital warts.
Cervarix
Cervarix is a bivalent vaccine which protects against the two high risk types of HPV: -16 and -18. Cervarix protects female 10 to 25 against precancerous conditions of the cervix and cervical cancer. It, however, does not protect against genital warts, nor it is approved for use for males.
Gardasil 9
Gardasil 9 is the newest approved HPV vaccine welcomed in Canada, it protects against nine different HPV types: -6, -11, -16, -18, -31, -33, -45, -52 and -58. It protects females between the ages of 9 to 45 against precancerous conditions of the cervix, vagina and vulva and cervical, vaginal, vulvar cancers and other as well. In females and males between 9 and 26 years of age, Gardasil helps prevent precancerous conditions of the anus or anal cancer. Gardasil 9 also protects males between 9 and 26 and females between 9 and 45 against anogenital warts.
Are the vaccines effective?
Studies show that Gardasil, Cervarix and Gardasil are very effective in preventing infection from the types of HPV they target. Cervarix is not approved for the prevention of precancerous conditions of the vagina, vulva or anus. Certain research also shows that the vaccines may be able to provide partial protection against other high-risk types of HPV, such HPV -31, -33, and -45, which are similar to -16 and -18; this is called cross protection, but more research is needed to verify the effectiveness and duration of this vaccine against these other HPV types.
The National Advisory on Committee Immunization, a group which makes recommendations for the use of vaccines and identifies subsets of the population which are at risk for certain diseases that can be prevented with vaccines, had released their most recent recommendations on HPV vaccination in 2015, but so far no recommendations have been made so far for Gardasil 9.
Vaccination of girls and women
NACI recommends that either HPV vaccine (Gardasil or Cervarix) be given to prevent precancerous cervical changes and cervical cancer and in:
- Females 9–26 years of age—the vaccines are most effective when administered to females before they are sexually active
- Females 15–26 years of age who have been sexually active, have contracted genital warts or had previous abnormal Pap tests, including cervical cancer—vaccination could still help this population because they may have not been infected with the HPV types the vaccine protects against
- Females over 26 years of age—the effectiveness of Cervarix has not been directly tested on this age group, but there is some evidence from immune responses in younger women to suggest that the vaccine may have similar effectiveness in older women
Only Gardasil is approved for girls and women aged 9–45 to prevent vaginal and vulvar cancer and their associated precancerous conditions, as well as anal and genital (anogenital) warts; Gardasil is also the only vaccine approved for girls and women ages 9–26 to prevent anal cancer and its precancerous conditions.
Vaccination of boys and men
Only Gardasil is approved for boys and young men to prevent anal cancer and its associated precancerous conditions and anogenital warts. The vaccine is most effective when given to males before they become sexually active. NACI recommends that Gardasil be used for:
- males between 9 and 26 years of age
- males 9 years of age and older who have sex with other males
There is some evidence that Gardasil may also prevent penile, perianal and perineal precancerous conditions (intraepithelial neoplasias) and their associated cancers, but it is currently not approved for this use.
Research is being done to see if vaccinating boys and young men before they become sexually active can prevent them from passing on HPV to females. In turn, this could help reduce cervical cancer risk in women. The National Advisory Committee on Immunization (NACI), which helps to shape public policy, recommended in 2012 that the HPV vaccine should be provided to boys, just as it is to girls [29].
Currently, while all provinces and territories have voluntary, school-based vaccination programs for girls, only Nova Scotia, PEI, Alberta and BC currently have similar vaccination programs for boys. The Ontario Ministry of Health says it’s ‘reviewing’ the current program to determine whether changes are required [30].
References
[27] “HPV Vaccines.” Canadian Cancer Society. Canadian Cancer Society, 2015. Web. 12 Aug. 2015.
[28] “HPV Shot Offers ‘herd Immunity’ to Unvaccinated.” CBC News. CBC/Radio Canada, 09 July 2012. Web. 15 Sept. 2015.
[29] ibid.
[30] Ruryk, Jackie. “HPV Vaccine: The Growing Campaign for including Boys.” CBC News. CBC News, 30 June 2015. Web. 15 Sept. 2015.
[31] ibid.