New vaccines against two common sexually transmitted viruses may reduce their transmission rates significantly. Although larger trials have yet to be completed, the initial results--published 21 November in The New England Journal of Medicine--have thrilled infectious disease experts and doctors.
Human papilloma virus (HPV) causes genital warts and cervical cancer and infects about 20% of adult U.S. women. The new vaccine targets a version of the virus called HPV-16, which has been linked to 50% of cervical cancer cases and suspicious pap smears. Epidemiologist Laura Koutsky of the University of Washington, Seattle, and colleagues injected a synthetic version of the virus's protein shell--which normally houses the virus's DNA--into 768 women. Another 765 women received a placebo injection. After 7 months, none of the vaccinated women had persistent infections of HPV, whereas 3.8% of the women in the placebo group did, indicating a remarkable 100% efficacy.
The second vaccine is for herpes simplex virus-2 (HSV-2). The sexually transmitted virus sometimes creates painful genital blisters, but 80% to 90% of the people who have it have no symptoms. The virus can be transmitted to babies if the mother is shedding virus during labor; left untreated, HSV kills about half of its newborn victims. Researchers have been attempting to make an HSV vaccine for more than 50 years, with no luck.
To create the new vaccine, researchers combined one of the proteins that make up the herpes virus shell with a compound that helps the immune system cells fight infections. About 73% of the women injected with this vaccine were protected from HSV-2. But to the researchers' surprise, the vaccine did not work in men. It also did not protect women who were already infected with HSV-1--the herpes virus that causes cold sores in up to 90% of adults. Even so, says lead author Lawrence Stanberry of the University of Texas Medical Branch in Galveston, over time the vaccine could stem the current rise in new infections, even in men, as the number of infected women decreased.
Larger studies are currently under way with both vaccines. Pathologist Christopher Crum of Brigham and Women's Hospital in Boston likens the HPV vaccine result to the discovery of the poliovirus vaccine. Likewise, infectious disease researcher Thomas Heineman at St. Louis University, Missouri, says the herpes vaccine "is exciting news. I had to read [the paper] twice to convince myself that this was as good as they say."