A new study from GlaxoSmithKline reveals that, in preliminary tests, an experimental vaccine was 100 percent effective in protecting women against repeated infection by two strains of human papillomavirus. "The vaccine breaks new ground in the battle to prevent the spread of sexually transmitted diseases," said John Schiller of the National Cancer Institute. According to Schiller, the vaccine, which is administered in three doses, may be able to prevent as many as 75 percent of 500,000 cases of cervical cancer reported each year. If it receives all the necessary approvals, the vaccine could be on the market in three to five years.