Luisa Villa, of the Ludwig Institute for Cancer Research in Sao Paulo, Brazil, gave a sneak peek of the vaccine study last week at a scientific meeting in New York City, where she spoke to WebMD. She announced her results publicly today at a conference in Paris, France.
The study shows that the vaccine protects women against cancer-causing types of the human papilloma virus (HPV). HPV is responsible for about 95% of all cases of cervical cancer. More than 100 strains of the virus exist, but the vaccine is designed to work against just four of them -- HPV 6, 11, 16, and 18. Types 6 and 11 cause genital warts. HPV 16 and 18 are responsible for about 70% of all cervical cancers. All of these types are transmitted sexually.
More than 1,100 women, aged 16-23, were injected with the vaccine or a placebo three times over six months. Each woman who got the vaccine had a strong immune response against the virus. No one who got the placebo was protected.
The vaccine also appears to be quite safe. The only side effect Villa saw that differed much from the placebo was in one woman, who developed a fever.
This was second phase of human trials, and the vaccine is now moving into the final phase of testing. Over the next two to three years, Villa and her colleagues will see how long the protection lasts. If women stay immune to HPV for long enough, large-scale vaccination programs could begin.
Girls could get the vaccine when they become sexually active, and therefore become vulnerable to HPV, but settling on an appropriate age could be tricky. Age 18 might be too late, but age 12 or 13 might be too young. Most girls in the U.S. aren't having sex then. The issue could be avoided by adding the vaccine to the battery of inoculations given in early childhood. "If we can demonstrate that by vaccinating early in life you can get protection till the time where we get sexual activity, [that] could be one way," Villa says.
"At the moment, I think the important thing is to determine whether the vaccine works. Until you know the vaccine works, there's not much point in worrying about how to deliver it," says Ian Frazer, HPV researcher at the University of Queensland in Brisbane, Australia. Nevertheless, he says, "All the data to date show that this is going to be an effective vaccine."
Even if it is a success and millions are immunized, it wouldn't be the end of HPV vaccine research. It would not help women who are already infected. What's more, other types of HPV cause 30% of all cervical cancers. This vaccine isn't designed to protect against those.
An ideal vaccine would cover the vast majority of HPV types and cure infection in addition to preventing it. Frazer is working to create such a vaccine, but because it must be far more complex than Villa's vaccine, the work has been going slowly.
Eventually, it would be good to vaccinate men, too. "It's doable, if people put money behind it," Villa says.
If all men and women were vaccinated, HPV could be wiped out. "In principle, although I suspect not in practice, this is a virus that could potentially be eliminated the same way as we have eliminated smallpox," Frazer says.
For now, HPV will remain a major threat to women's health. Doctors urge women to get yearly Pap smears -- a test that looks for cervical cells that aren't normal, signaling the presence of HPV. These abnormal cells don't always turn into cancer, but they should be watched closely.