How to Kill a Cancer

Researchers have yet to determine how long the anti-HPV protection of any vaccine would last and how many lesions it would prevent. It's already clear that the Merck vaccine would not be of much help to women who have previously been exposed to HPV. For any mass-inoculation program to be effective, it would have to target girls and possibly boys before they become sexually active. This could prove a tough sell for parents, not to mention conservative politicians and proponents of abstinence. And, of course, any vaccine that contains only HPV-16 and HPV-18 would not protect against other strains of the virus that can cause cancer. So even after a vaccine is commercially available, most women will still need Pap smears.

Eventually, however, as fewer women become infected with the major cancer-causing strains of HPV, doctors may be able to eliminate or greatly reduce the need for Pap smears. That doesn't mean women can rest easy. The reason: new tests will still be needed to keep tabs on other strains of HPV that might supplant HPV-16 and HPV-18. When it comes to cervical cancer, early detection still saves lives. --Reported by Janice M. Horowitz and Alice Park/New York