A vaccine against cervical cancer could be available within five years and may eventually lead to the eradication of the disease in Britain, a scientist said.

Clinical trials are under way to protect women against the human papilloma virus (HPV), a sexually transmitted infection that causes almost all new cases of cervical cancer in this country. Dr Jack Cuzick, the head of mathematics, statistics and epidemiology at the Imperial Cancer Research Fund, said early results from international trials had been positive and there were grounds for further optimism.

"Early results have given no reason for concern, although there are a lot of hurdles ahead. Realistically, within three to five years we should know whether the first round of vaccines are good enough to license for use." Dr Cuzick said an effective vaccine raised the possibility of controlling cervical cancer by routine vaccination of teenage girls, rather than by the present approach of screening women.

"If these trials prove successful, it may be possible to vaccinate girls in their adolescence against the human papilloma virus. Eventually, this could lead to the eradication of cervical cancer," he said.

Cervical cancer is the second most common form of cancer among women worldwide, with 500,000 cases annually, leading to 300,000 deaths. In Britain, there are 3,000 new cases and 1,300 fatalities a year.

Women who have unprotected sex with multiple partners, and teenagers who become sexually active at a young age are at greater risk of contracting the disease.

Dr Cuzick said the vaccine worked by "producing large numbers of antibodies, which are programmed to detect the HPV virus and infected cells so that they can be eliminated".

Researchers were not yet sure whether girls aged 13 to 15 should be immunised before they had any contact with HPV through sexual intercourse or whether the vaccine was just as effective in women in their early 20s who had already been introduced to the HPV infection.

Dr Cuzick said cervical screening had been a "real success story" in Britain, reducing death rates among women under 55 by 60 per cent and saving 6,000 lives between 1991 and 1997. But screening was not viable in developing countries, so vaccination might offer hope.

* A new clinical trial to find the most effective form of chemotherapy for the growing number of women diagnosed with advanced ovarian cancer was announced yesterday.

Ovarian cancer is now the fourth most common form of cancer among British women, with a rise in its incidence over the past two decades of between 20 and 25 per cent.

But it is often diagnosed when the disease is at an advanced stage and five-year survival rates across the UK are "worryingly low" compared with other Western European countries.

In Britain, 4,500 women die each year. Only 29 per cent of patients are alive five years after diagnosis compared with 45 per cent in Sweden and Austria and 41 per cent in Spain.

Researchers believe that the trend of having children later in life, unhealthy diets and obesity are behind the growth in ovarian cancer, which is found in 6,500 women a year.

The new study, co-ordinated by the Medical Research Council, will look at five different combinations of chemotherapy to find out which is the most effective and look at the genetic factors behind the disease.