@ Amethyst some interesting facts and studies.
Human papillomavirus (HPV) vaccines are intended to be prophylactic, not therapeutic. Protection rates are lower in women who have already been infected with the vaccine-related genotypes [WHO, 2007] . It is therefore important to vaccinate girls before they become sexually active [DTB, 2008; (Drug and Therapeutics Bulletin)]. The National Childhood Immunization Programme offers immunization for girls of 12–13 years of age [DTB, 2008; DH 2012].
Controlled trials have indicated that the HPV vaccine Gardasil® (quadrivalent) is highly effective at preventing susceptible women from being infected with HPV types 6, 11, 16, and 18 [WHO, 2007; DH, 2012].
Studies found:
- 90% fewer persistent infections with genotypes 16 or 18 [DH, 2012].
-That the HPV vaccine is over 99% effective at preventing pre-cancerous lesions associated with HPV types 16 and 18 in young women. Studies suggest that protection is maintained for at least 7 years, but the results of long term follow-up studies are awaited.
Gardasil® is the vaccine of choice for the national immunisation programme as this vaccine is also 99% effective in preventing genital warts associated with HPV types 6 and 11 in young women .
A multi-site study of HPV type-specific prevalence in women with cervical cancer, cervical intraepithelial neoplasia, and normal cervical cytology in England found that non-vaccine HPV types (that is types 16 and/or 18 ) were found in 60% of women with mild dyskaryosis or less, but in fewer than 20% of women with cervical cancer. The authors commented that these results suggested that the HPV vaccine should have a marked impact on cervical disease in England [Howell-Jones et al, 2010].
It is not known how long protection lasts and whether booster doses are necessary [DTB, 2008] . Levels of antibodies to HPV are low or non-existent after infection, because HPV only has a mucosal phase and not a bloodstream phase. Levels of antibody after vaccination are much higher than after natural infection. This differs from other viral vaccines, and therefore it is not possible to predict from experience the expected length of time for protection against HPV infection [WHO, 2007]
.- A follow-up study of 383 women who had received three doses of HPV-16/18 virus-like particle vaccine and 393 women who had received a placebo found sustained high levels of antibodies at 4.5 years of follow up [Harper et al, 2006].
- A follow-up study of 17622 women who had received the quadrivalent vaccine found that the vaccine had provided sustained protection for 42 months [The Future I/II Study Group, 2010].
There is some cross-protection against other genotypes from both the bivalent and the quadrivalent vaccines[WHO, 2007; DH, 2012].
Bivalent vaccine: cross-protection demonstrated against two other genotypes has been demonstrated in HPV-naive women.
Quadrivalent vaccine: neutralizing antibodies against genotypes 31 and 45 have been demonstrated.
As with any vaccine there are unknowns but they do save lives and that's the overriding factor. So it's a choice that we make.
An interesting side note regarding males and the HPV vaccine.
This is an often an overlooked fact that males can be vaccinated against the HPV. If you are 26 or younger, there is an HPV vaccine that can help protect you against the types of HPV that most commonly cause problems in men. The HPV vaccine (Gardasil) works by preventing four common HPV types, two that cause most genital warts and two that cause cancers, including anal cancer. It protects against new HPV infections; it does not cure existing HPV infections or disease. It is most effective when given before a person’s first sexual contact .
In fact the CDC recommends the HPV vaccine for all boys ages 11 or 12, and for males through age 21, who have not already received all three doses. The vaccine is also recommended for gay and bisexual men, and men with compromised immune systems through age 26, if they did not get fully vaccinated when they were younger.