A new paper to be published in BJOG: An International Journal of Obstetrics and Gynaecology outlines a number of ongoing questions and challenges related to HPV vaccination. These include the decision to limit vaccination to adolescent girls, and the importance of continued screening.
In 2008, the government launched a nationwide immunisation programme designed to protect British women against the devastating impact of cervical cancer.1 Cervarix, the vaccine chosen in the UK, offers protection against human papillomavirus (HPV) types 16 and 18, which together are responsible for approximately 70% of cervical cancers.
Considerable debate has surrounded the fact that all national vaccine programmes have limited their target population to adolescent girls. The authors explain that as the purpose of HPV vaccination is the prevention of cervical disease, vaccinating girls alone is sufficient to achieve linear reduction in prevalence of HPV amongst girls, and a non-linear reduction in prevalence amongst boys.
However, the paper notes that one of the problems of a sex-specific vaccine is that it may fail to educate males about their role in transmitting the virus. HPV vaccination may also reduce the incidence of other, less common cancers linked to HPV infection, such as vulval, vaginal, penile, anal and oropharyngeal cancers. Men who have sex with men are particularly at risk of anal and oropharyngeal cancers.
In developing countries, there may be a better case for vaccinating young men, as in some settings increased coverage of young women may not be possible beyond a certain threshold. In resource-poor countries, some young women may not be reachable by the vaccination programme, due to poor school attendance for girls, early marriage (and consequent early onset of sexual activity) and lack of parental consent for vaccination.
The authors note that there are still many unanswered questions about the long-term cost-effectiveness and safety of both of the current HPV vaccines. In the UK there has also been criticism of the choice of vaccine.2 The paper notes that in general, both CervarixTM and Gardasil® appear to be safe and well tolerated.
Key recommendations highlight the importance of continued cervical screening for all women. Up to 30% of cervical cancers are caused by HPV types not included in either vaccine. As such, vaccinated women are still at risk of contracting other HPV types that can cause cervical cancer.
Lead author, Dr. Emma Crosbie, from the School of Cancer and Imaging Science, University of Manchester, said “The school-based HPV immunisation programme has been very well received overall, with uptake figures as high as 80-90% in some areas of the UK. Maintaining good coverage is essential if we are to achieve a significant reduction in the incidence of cervical cancer in years to come.
“In addition to girls currently aged 12 to 13 years, those up to the age of 18 have been offered the vaccine as part of a one-off ‘catch-up’ programme. This ‘catch-up’ programme has largely been delivered through Primary Care Trusts and uptake figures reflect the varied success that individual practices have had in inviting eligible girls to attend for vaccination. Current evidence suggests that, unless previously infected with HPV 16 or 18, vaccination is likely to be just as effective in this group of young women as in their pre-adolescent counterparts.”
Pierre Martin-Hirsch, BJOG scientific editor, said “HPV vaccination is an important way to reduce the risk of cervical cancer. I would strongly encourage parents and girls who are of age to take up the offer of the HPV vaccine.
“Regular cervical screening will continue to be important. All women should attend cervical screening when invited, and ensure that arrangements for regular periodic appointments are made. With regular screening, cervical cancer is preventable.”
Ends
Notes
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This paper will be published in the BJOG theme issue in January 2010, "The gynaecological and reproductive health problems of puberty and adolescence."
1 In future, girls aged 12-13 years will be immunised each year as part of the routine National Health Service immunisation programme. In addition, all girls aged 13-18 years are being offered the vaccine in a ‘catch-up’ programme. This will ensure that by 2011 the 12-18-years cohort will all have been invited for free HPV vaccination.
2 The UK Health Authority and the Netherlands have chosen CervarixTM, a bivalent vaccine that protects against the two strains of HPV responsible for 70% of cervical cancers (HPV types 16 and 18), but does not prevent genital warts. The USA, Canada, Australia, New Zealand, Spain, France, Switzerland and Sweden chose Gardasil®, a quadrivalent vaccine that confers immunity against the HPV types 16 and 18, as well as two strains that together cause 90% of genital warts (HPV 6 and 11).
Reference
Crosbie E, Brabin L. Cervical cancer: problem solved? Vaccinating girls against human papillomavirus. BJOG 2009; DOI: 10.1111/j.1471-0528.2009.02369.x.
To view an abstract of the paper, click here.
