A new vaccine protects nine out of ten women against cervical cancer linked to two strains of the deadly human papillomavirus (HPV), according to a study published Thursday.
HPV types 16 and 18 account for 70 percent of cervical cancer cases worldwide, which number about 500,000 per year, according to the UN Population Fund (UNFPA).
If left untreated, invasive cervical cancer is almost always fatal.
In a clinical trial, more than 9,000 women were vaccinated with the experimental drug, with a control group receiving a vaccine for hepatitis A.
Over a 15-month follow up period, the drug showed a 90.4 percent efficacy against the kind of pre-cancerous lesions that are a precursor to full-blown cervical cancer.
"The vaccine is effective, well-tolerated and immunogenic" -- meaning it produces an immune response -- "in a broad population of young adult women," said University of Helsinki professor Jorma Paavonen, who led the study.
Side-effects were minimal, the study found.
The drug being tested, which has yet to go to market, would be sold under the brand name Cervarix, and is manufactured by British firm GlaxoSmithKline, which funded the study.
A similar drug produced by US firm Merck, Gardasil, also vaccinates against HPV types 16 and 18, and has already been approved for sale in many countries.
More than half of the women vaccinated in the phase III trials were from Finland, with the rest coming from 13 other countries, including many in the developing world, where 90 percent of new cases occur.
"The vaccine is not therapeutic but prophylactic," Paavonen said by telephone, explaining that it would not benefit women who already test positive for both of the targeting virus strains.
But those who were exposed to only one of the strains would be protected from the other, and even those who had been exposed to both "received some cross-protection from other strains," he said.
Cervical cancer is the second most common type of cancer among women, with deaths projected to rise by almost 25 percent over the next 10 years, according to the UNFPA.
Earlier this month the British government took steps towards vaccinating girls as young as 12 against the sexually-transmitted virus, a measure that could be implemented by late next year.