An HPV vaccine bonus
New studies of the cervical cancer vaccine Gardasil show that it provides some protection against additional strains of the human papillomavirus, or HPV, beyond the four strains targeted.
The two studies were designed and sponsored by Merck Research Laboratories. Merck & Co. produces the vaccine. Both studies will be published in the April issue of the Journal of Infectious Diseases.
The vaccine was designed to block four strains of HPV, which are associated with about 70% of all cervical cancers and 90% of genital warts.
In one study, Dr. Darron R. Brown of the Indiana University School of Medicine, found that Gardasil provided some protection against an additional 10 HPV strains that together are responsible for about 20% of cervical cancers. Brown studied 17,622 women aged 16 to 26 who had not previously been exposed to the viruses and found that Gardasil reduced the incidence of precancerous changes in cervical cells by 32.5%.
A second study, by Cosette M. Wheeler of the University of New Mexico Health Sciences Center, looked at the vaccine's effect against the same 10 strains in a group that included women who already had HPV infections. In the second study, the vaccine reduced precancerous cell growth by 15%.
It was already known that the vaccine works best when given before a young woman is sexually active and may have already contracted the virus, which is why the national Centers for Disease Control and Prevention recommends it for 11- and 12-year-old girls, up to age 26. The second study showed that the bonus coverage extended, though not as strongly, to young women who already were sexually active.
Hailed by some as a breakthrough in women's health and in the war against cancer, Gardasil -- or more specifically, the CDC's recommendation -- has been greeted more skeptically by others. Critics say that the vaccine, approved in June 2006, is too new for its long-term effectiveness and safety to be judged. Others say that it's too expensive and that it's unnecessary because an effective cervical cancer screening method, the Pap smear, already exists.
In an editorial in the same journal, Dr. Rolando Herrero of the Proyecto Epidemiologico Guanacaste in Costa Rica, said that the vaccine -- and the broader protection it may offer -- is especially important in parts of the world where regular Pap screening tests are not available, but vaccination programs are.