It would be the second vaccine against a major human cancer, following a hepatitis B vaccine that prevents primary liver cancer.

If successful, it could pave the way to defeat for the second most prevalent cancer among women. Breast cancer is the first.

WHO scientists were meeting this week in Geneva to take stock of developments. On Friday they said there are several candidates for such a vaccine.

Tackling a global problem

There are 500,000 new cases of cervical cancer each year, and nearly 300,000 deaths annually, according to the WHO.

Eighty 80 per cent of these occur in developing countries.

Scientists believe that essentially all cervical cancer is caused by infection with a few types of human papillomavirus (HPV).

Scientists looking to develop a vaccine have approached the problem from different angles, but have mainly focussed on genetically-engineered VLPs (virus-like particles).

These are not infectious and cannot cause cancer because they contain no DNA.

Some of the research groups are looking at creating a vaccine that prevents the cancer developing at all.

Others are developing vaccines that would prevent recurrence of cancer or tackle it once it has developed.

Hurdles before the finishing post

The scientists said they all faced "huge obstacles".

Part of the reason for this is that their experimentation is limited, because fully infectious HPVs are harmful.

The meeting agreed that a preventive vaccine should have priority.

Ideally this could be targeted at a young population that is not yet sexually active, although older people may also benefit from such a vaccine, they said.