Vaccine May Prevent Cervical Cancer
Many women who are infected with HPV don't know it, and studies show that the average woman is infected for about 10 years before cervical cancer develops, says Hildegund C.J. Ertl, MD, PhD. "Most women when they get infected with the [HPV] virus simply get rid of it, but there is a small fraction of women that don't, and they become persistently infected," says Ertl, a professor and vaccine researcher at the Wistar Institute in Philadelphia.
She says the new vaccine research is a promising first step but cautions that it will be years -- probably as many as 10 years -- before an actual vaccine is available to the public. Right now, the experimental vaccine being used in the studies only protects against HPV16, but there are three other types of HPV that also have been linked to cervical cancer. Lowy says his group will continue to do studies with the vaccine that protects against the most common type and may eventually expand it to protect against the others.
Another question that still remains is whether people will need frequent reimmunizations, or boosters, to maintain high levels of protection against HPV. Lowy says longer studies are needed to determine how long the initial shot will last. "We don't know right now whether the protection will be for one year or 10 years," he says.
Meanwhile, other researchers reporting in the same issue of the medical journal say they've discovered that HPV16 is more complicated than originally thought. A study of more than 10,000 women in Costa Rica suggests that HPV16 has individual strains, or variants, some of which may be up to 11 times more likely to cause cancer than others. That's not to say HPV16 has much good going for it, though, since previous research indicates that having any form of HPV16 infection increases the risk of cervical cancer by more than 700 times.
Cervical cancer is diagnosed by a Pap smear. However, about 2-5% of women who have Pap smears each year get back a result that is borderline -- meaning that it could be an early stage of cancer or it could be nothing to worry about, but it can't be confirmed. Although the vast majority will have nothing wrong with them, doctors don't agree about how to handle these cases, so many women undergo excessive testing or are told to come back for repeat Pap smears in a few months.