BioEd Online

The pharmaceutical company Merck made headlines last week with news that a few jabs in the arm can protect women from cervical cancer. The claim comes from the largest medical trial so far to test this type of vaccine.

The company has been in competition with GlaxoSmithKline, which also has a vaccine for cervical cancer called Cervarix now in trials (see ' Experts inject reality into cervical cancer prevention schemes' ).

The announcement of Merck's phase III results, which look at the protective power of their vaccine Gardasil for young women, brings a marketable vaccine much closer: Merck says their vaccine could be available as early as 2006.

The vaccine protects against the human papilloma virus (HPV), the sexually transmitted virus that causes cervical cancer. Importantly, it guards against HPV-16 and HPV-18, the two most dangerous strains that account for 70% of such cancers.

However, scientists caution that because the trial only lasted two years, it is unclear how long it protects against infection for. But the results, they add, have been impressive. Vaccines could cut the need for routine smear tests to detect this cancer, which claims the lives of 290,000 women worldwide each year.

Protective power

Merck's trial followed more than 10,000 women aged 16 to 26. Half of the participants followed the complete vaccine regimen of three jabs, the other half were given placebo shots.

None of the vaccine recipients were diagnosed with cancer associated with these types of HPV. In contrast, 21 cases of such cancer occurred in those given a placebo.

Even a single jab proved to be 97% effective in preventing cervical cancer from these types of HPV. The team also saw a boost in antibody production in the vaccine recipients.

Researchers presented the results last week at the annual meeting of the Infectious Diseases Society of America in San Francisco.

It remains unclear how long the vaccine will protect the women for, says Kevin Ault, a gynaecologist at Emory University in Atlanta, Georgia, who helped to lead the study. But he adds that women in their twenties are among those with the highest risk of developing cervical cancer, because smoking and other sexually transmitted diseases seem to make young women more vulnerable.

The vaccine contains empty protein shells of the human papilloma virus, which trigger the immune system to generate protective antibodies. According to Ault, vaccines can prompt the body to churn out 30-80 times the amount of protective antibodies produced by a natural HPV infection.

But the success of the trials also puts the spotlight on related ethical concerns: the cost of delivering such preventative drugs could make them inaccessible to developing nations. And convincing families in traditional cultures to vaccinate their daughters against a sexually transmitted virus such as HPV presents a hard challenge. Some critics also suggest that the vaccine, which is likely to be administered to girls as young as 10 to 13, could encourage underage sex.