Professor Henry Kitchener explains why boys should be included in the HPV vaccination campaign
The demonstration that prophylactic vaccination against HPV types 16 and 18 can prevent the majority of high grade cervical pre-cancers is one of the most significant clinical developments of the 21st Century.
It is expected that current vaccines would prevent 70% of cervical cancers in a vaccinated population. Such primary prevention of cervical cancer, which kills over 200,000 women annually worldwide, would avoid an enormous amount of suffering, particularly in under developed countries.
In well resourced countries, with secondary prevention in place, i.e. cervical screening, vaccination against these two HPV types will greatly reduce referral for colposcopy and will avoid the need for treatment of the majority of cervical pre-cancers detected as a result of screening. It is also hoped that it will further reduce deaths from cervical cancer.
The UK Government acted rapidly to put a national schools based HPV vaccination programme in place in 2008, targeting 12/13 year old girls in order to preclude the acquisition of HPV infection of the lower genital tract. This has been a widely acknowledged success, with over 80% uptake and it is clear that the large majority of parents have appreciated the benefit of this preventative strategy.
The vaccine selected for the first five years of the programme was Cevarix (GSK), a bivalent vaccine targeting types 16 and 18 and with published evidence of some cross protection against types 31, 33 and 45 it could be expected to prevent over 80% of CIN3. The safety record of the vaccine has been excellent.
A frequently asked question is what about vaccinating boys? Penile cancer, which is also caused by HPV is rare, but oro-pharyngeal cancer is also associated with HPV16, as is anal cancer, not uncommon in men who have sex with men (MSM). Far more common than these cancers is genital warts, with around 70,000 cases per year in England and Wales in males and 90,000 in females1.
These genital warts are caused mainly by HPV types 6 and 11. A rare but potentially lethal condition is respiratory papillomatosis, which is due to type 11 and can be transmitted to neonates at birth.
The other licensed prophylactic vaccine, Gardasil (Merck), is a quadrivalent vaccine targeting types 6 and 11 as well as 16/18, and this has been shown to have over 95% vaccine efficacy against genital warts.
Evidence that a national programme of vaccination of teenagers has an effect on the incidence of genital warts in the general population has been reported from Australia2, where females aged 9-26 had been offered the vaccine free of charge from 2007 up until 2009. Genital warts, as a proportion of new referrals in a large network of sexual health clinics, has fallen by 60% in females since the establishment of vaccination using Gardasil.
There has also been a lesser but significant fall in heterosexual males, suggesting a herd immunity effect. Because the incubation period for the development of genital warts is only three months, the effect on warts can be seen many years before any effect on cervical pre-cancer and cancer.
As the UK programme has switched to Gardasil because of the expected impact on genital warts, should boys be offered the vaccine?
In terms of cancer prevention, vaccinating only girls is more cost effective, but given the prevalence of genital warts, vaccinating boys as well could be cost effective given the healthcare resources consumed by the treatment of genital warts, not only that, boys would be as entitled to vaccination, and the effect on herd immunity would be considerable.
One consequence of offering vaccination to prevent genital warts could be greater difficulty in gaining public support for a vaccine which prevents a sexually transmitted disease. If this affected female uptake, the anticipated impact on cervical cancer prevention could be reduced.
Male vaccination could also be expected to reduce the incidence of oro-pharyngeal cancer, as well as anal cancer, especially in MSM, though this risk factor only becomes apparent later in life. Given the safety of the vaccine and its ability of prevent genital warts in a public health programme, the negotiated cost becomes key.
It does seem likely that an HPV vaccination programme based on Gardasil would have to include boys, for whom it is licensed, but just as happened with female vaccination with the bivalent vaccine, careful work will be required in developing information and messages to retain a high degree of public acceptance.
Professor Henry Kitchener is professor of gynaecological oncology at the University of Manchester and Chair of the Advisory Committee for Cervical Screening. The views expressed in the article are his and in no way represent those of the Department of Health.
1. Health Protection Report Vol 5, No 17, 28 April 2011 (accessed 4 October 2011).
2. Donovan et al (2011). Quadrivalent human papillomavirus vaccination and trends in genital warts in Australia: analysis of national sentinel surveillance data. Lancet Infectious Disease; 11: 39-44.