Vaccinating girls against HPV
The joint committee on vaccination and immunisation, the independent body which advises the government on vaccines, has concluded that there is sufficient evidence for the protective effect of vaccination against human papilloma virus (HPV) to recommend it for girls at around 12 years of age. The Department of Heath has agreed in principle and vaccination is expected to begin in 2008.
Some types of HPV are associated with a number of benign skin conditions, such as genital warts and verrucae, and other types are known to be associated with cervical and other types of cancer. For example, types 6 and 11 cause anogenital warts and some low-grade neoplastic lesions, while types 16 and 18 are the cause of the majority of cervical cancers worldwide.
There is a growing body of evidence to suggest that vaccination can prevent new wart infections and precancerous cervical lesions associated with HPV types 16 and 18. An interim analysis published recently finds a bivalent vaccine against these two types both effective and safe.1 Another recent trial reported on the efficacy of a quadrivalent vaccine against HPV types 6, 11, 16 and 18.2
The debate is not about whether the vaccine is effective, but about who should be vaccinated, and when. The HPV types that cause cervical cancer are sexually acquired. This means that the vaccine has to be given before any risk of exposure;in practice, before adolescence. This has caused controversy in conservative societies, including some states in the USA. Those who advocate abstinence in young people are concerned that HPV vaccination will condone or promote sexual promiscuity. However, we already know that the onset of sexual activity does not have a single cause, for example the availability of contraception. Other determinants include peer pressure, societal norms and educational achievement.
For most interventions involving children aged below 16 years it is appropriate to seek consent from a parent or legal guardian; however, children may also give valid consent if they are considered capable of making the decision. This gives rise to some interesting ethical considerations. If the parent and young person both refuse, how far should the healthcare professional go in trying to educate them? If an adolescent girl wishes to be vaccinated because she is, or intends to be, sexually active, but her parents refuse in the belief that she is not sexually active, whose wishes are paramount?3 This may raise similar issues as prescribing contraception or giving sexual health advice to patients under 16 years of age.
Many published trials use young women as subjects, and vaccines may not be licensed for use in young men. It may be very difficult to prove beyond modelling studies that vaccinating young men and boys has much effect on the primary outcome measure of reduction in precancerous cervical lesions in women. Although early phase trials have found HPV vaccines to be safe, there are no data on safety in the longer term.
HPV is not as contagious as influenza, measles or polio and yet, compared with the vaccines for those diseases, HPV vaccines are expensive. Should their use be limited, therefore, to individuals at high risk? There are questions, too, as to how a mass immunisation programme for HPV should be implemented. We have very little information on the impact of vaccination on other HPV types.
We do not know if there are likely to be benefits in a catch-up campaign of vaccination in adults who are already exposed to HPV.
Although these important questions have yet to be resolved, there is no doubt that HPV vaccines can save lives and reduce much of the physical, psychological and psychosexual morbidity associated with cervical abnormalities.
I am hopeful that we will see an HPV immunisation policy that is supported by evidence and acceptable to the public, and which will relegate cervical cancer to the history books within decades.Dr Richard Ma Author
Dr Richard Ma
MBChB MSc DCH DRCOG DFFP DipGUM MRCGP
GP principal, North London and staff grade in sexual and reproductive health, Margaret Pyke Centre, London