"I want the one for older women" — extending the human papillomavirus vaccine population base

To the Editor: Wain’s criticism of the Australian Therapeutic Goods Administration (TGA) approval of the bivalent vaccine, Cervarix (GlaxoSmithKline), suggesting it did not adhere to World Health Organization guidelines,1 should not detract from the potential benefits of human papillomavirus (HPV) vaccination in women over 26 years of age.

An immunogenicity study showed all women up to the age of 55 years seroconverted to both HPV types and, while mean antibody concentrations at Month 7 were lower than in the younger age group, they were still three to four times higher than those observed in 15–25-year-old women in the long-term follow-up study (up to 4.5 years after vaccination), where continued efficacy was demonstrated.2 HPV infection is most prevalent in younger age groups, with one study showing a prevalence of 44.8% in women aged 20–24 years.3 As indicated by Wain, the vaccine has diminished efficacy in populations with high rates of previous exposure. Thus, 20–24-year-olds would benefit least, and if we extrapolate his argument, should not be included in any catch-up vaccination program. The United Kingdom has, in fact, recommended a catch-up campaign for girls aged up to 18 years only. The prevalence of HPV infection decreases after 26 years of age, and these “older” women should benefit from vaccination as supported by preliminary efficacy data of the quadrivalent vaccine Gardasil (Merck) in an older population.4 This vaccine may also be protective for women who have been previously exposed to the same subtypes of HPV as the vaccines, as shown by 100% efficacy against cervical intraepithelial neoplasia (CIN) grade 2/3 or adenocarcinoma in situ (AIS) among people who are seropositive but HPV-DNA-negative to the relevant HPV type.5

The Pharmaceutical Benefits Advisory Committee initially did not recommend funding for Gardasil on the basis of cost-effectiveness until after an extraordinary meeting to consider a revised submission, following an “unusual” request from the Health Minister.6,7 CSL agreed to reduce the price, undertook to make a substantial contribution to any booster program if it became necessary in the next 20 years, and also to the costs of setting up a national register to link vaccination data to later cervical screening records.

It is obvious that the efficacy of HPV vaccines will inevitably be lower after commencement of sexual activity, but we believe that it is the medical practitioner’s responsibility to offer women aged over 26 years the current, albeit incomplete, information on vaccine efficacy, and allow women to make the choice.