Cervical cancer affects about 4,000 women annually in the UK, of whom about 1,200 die, though this number is falling. The cancer is spread by the wart virus, known medically as the human papilloma virus or HPV.

Although there are more than 70 types of this virus, only 13 are capable of causing cancer, and of this 13, only five types – 16, 18, 31, 33 and 45 – commonly do so. Of the cases of cervical cancer, 70 to 80 per cent are associated with an infection from HPV types 16 and 18. The virus, when it affects the cervix, is spread by sexual intercourse, but although more than 70 per cent of all women of reproductive age show evidence of having been infected with HPV, only in a very small minority of cases does the virus remain persistently on the cervix. Its presence can be detected by viral cultures and these are becoming increasingly important in determining which women are in danger of developing cancer.

There is evidence that early infection is likely to lead to a persistent infection and possible malignancy later. This is more likely to result from sexual intercourse early in teenage years. A woman also runs a greater risk if HPV cultures persist in her cervix after the age of 30. Risk of cervical cancer is therefore related to the age at first intercourse as well as to the number of sexual partners a woman has over her lifetime. The sexual histories of her partners are also highly relevant and, for other reasons, so is whether the woman is a smoker.

There is often a long interval between initial infection and the development of malignant or premalignant changes on the cervix that may lead to death. The most common age for a woman to die of cervical cancer is in her early fifties. As a girl’s age at first intercourse is falling, the early vaccination of girls is essential if the death rate for this disease is to be reduced.

Many doctors believe that the vaccination programme should be extended to both boys and girls before puberty.Adding weight to that argument is that HPV is responsible for cancers besides those of the cervix. The same types of HPV virus can be shown to be the likely origin of many cases of penile cancer in men, and of anal and oral cancer in both sexes.

Some authorities attribute the large increase in oral cancer over the past 30 to 40 years to changes in sexual habits and the increasingly common practice of oral sex. For these reasons, most doctors will welcome the Government’s announcement of a vaccination programme for girls. They will, however, be keen to see the programme extended to reach older females earlier than has been announced, and, because of the variety of cancers caused by HPV, to boys and men as well.