The National Health Service has begun assessing how many young women will enter in the Government human papilloma virus (HPV) immunization program.

The Government announced a routine immunization of all school girls aged between 12 and 13 for next September. Also, the program will include, until 2009, girls that will be then aged 18.

This program comes after a recommendation from the Joint Committee on Vaccine and Immunization (JCVI) to use this new HPV licensed virus, which in trials has proved to prevent at least 70 percent of cervical cancers. It is expected that, in time, the number of cervical cancers will decrease with 400 cases per year.

The vaccine is marketed as Gardasil, made by Merck, and Cervarix, made by GSK. These two manufacturers are competing for the Government contract.

This vaccine can be offered by private clinics for up to £500 and administrated in three doses in six months. The Government program is expected to lower the vaccine price.

The vaccine protects against 70 percent of HPV strains. This means there are still 30 percent chances for cervical cancer.

Researchers say that women under 30 naturally clear HPV infection. This vaccine is effective in women who are not already infected with HPV or have naturally got rid of it. HPV infection occurs from the start of sexual activity in adolescents and it has its peak during individuals’ twenties.

The vaccine, although possibly most effective on girls who haven’t begun their sexual lives, might also be of benefit to women aged 25 and older, depending on their level of sexual activity and exposure to the virus. Studies show that 25 percent of university age women are infected with HPV and there are the remaining 75 percent that might be helped with the vaccine.

Pamela Morton, of Jo's Trust, which has campaigned for the introduction of the vaccine, militates for extension of Government program for women also aged between 18 and 26.

Studies show that the vaccine will offer protection for the next 10 to 20 years.

The chief executive of Cancer Research UK, Harpal Kumar, said: "This is an exciting step towards preventing cervical cancer in the UK."