Q&A:The pros and cons of vaccination for girls against HPV, and the link between HPV and cervical cancer
What is HPV?
HPV stands for human papilloma virus - a sexually transmitted infection. It is estimated that almost 80 per cent of sexually active people have been infected with at least one type of the virus.
What is the link between HPV and cervical cancer?
Although there are in excess of 200 HPV strains, just a small number are associated with the development of cancer of the cervix (neck of the womb). HPV types 16 and 18 are found in almost 70 per cent of cervical cancers, while another five sub-types are responsible for a further 20 per cent of cases. HPV infection is found in 99 per cent of women with cervical cancer.
How common is cervical cancer?
Cancer of the neck of the womb is diagnosed in almost 200 women here every year. Some 70 women die from the disease annually. Cervical cancer usually develops quite slowly, passing through a number of pre-invasive stages (carcinoma in situ - CIN) before becoming an invasive cancer that spreads. If caught in the early stages, cervical cancer has a five-year survival rate of 80 per cent or greater.
Why might HPV vaccine help?
Because of the very strong link between HPV and cervical cancer, giving a vaccine to a woman before she becomes infected with the virus has the potential to hugely reduce the number of women at risk of cervical cancer.
Clinical trials have shown that HPV vaccination prevents advanced forms of non-invasive cervical cancer. However, because published data on the vaccine does not yet extend beyond a five-year follow-up period, it has yet to be scientifically proven that HPV vaccine prevents invasive cancer of the cervix.
When and how often is the HPV vaccine administered?
HPV vaccines, of which there are two on the market (Gardasil and Cervarix), must be given before the recipient becomes sexually active and contracts the virus. This means administering a comprehensive vaccination programme to girls aged 11 to 13. A full response requires three separate injections over six months. Because information is so far limited to a five-year follow-up period, it is not yet clear whether a booster vaccine will be needed. If it is, it is likely to mean a once-off additional injection.
How safe is the vaccine?
As with most vaccines, a local reaction at the injection site is quite common. Headache, fatigue and tummy upset have been reported following HPV immunisation. Fainting has occurred after vaccination, a common occurrence when immunising adolescents.
In the US, a possible association between HPV vaccination and Guillian-Barré Syndrome (a rare but acute neurological condition) is being investigated. In the US, three deaths were closely related in time to immunisation with a HPV vaccine, but no link could be found between the girls' deaths and vaccine administration. It is estimated that some 1.5 million people have been vaccinated with one of the commercially available vaccines in Europe.
Why has it been decided to target 12-year-old girls?
The Minister for Health has been advised on HPV vaccination by the National Immunisation Advisory Committee of the Royal College of Physicians of Ireland (RCPI) and by the Health Information and Quality Authority (Hiqa). The expert advice was to target those aged between 11 and 13, with a once-off catch-up immunisation programme for 13- to 15-year-old girls. A key element of the decision was to ensure immunisation took place before sexual activity, because once a girl has been exposed to the virus vaccination is ineffective.
But why not target girls up to the age of 18?
Although the expert advice, here and in the UK, was to immunise 12-year-olds annually and carry out a catch-up programme up to the age of 15, a political decision was made by the UK health secretary to have a catch-up programme for those up to 18. Minister for Health Mary Harney could have replicated that decision here, but for financial and resource reasons has confined the programme to an annual primary school-based programme aimed at 12-year-old girls.
Research suggests the average age at which Irish women become sexually active is between 17 and 23, although one survey found that 22 per cent of 18- to 24-year-olds reported sexual activity before the age of 17.
So, what choice do parents of 13- to 18-year-old girls have?
Following the announcement yesterday, there is no prospect of these adolescents receiving a free HPV vaccine from the State. Their only choice is to pay for the three-part vaccination and have it administered by their GP. The estimated cost of a course of private HPV vaccination is around €600.