T O R O N T O, Sept. 17, 2000 -- Researchers have made the first vaccine thatprotects against genital herpes. But there is a major catch: Itworks only in women and only if they have never had cold sores.
The findings, reported today, are a surprise. Until now, novaccine has ever been shown to work in one sex but not the other.Experts say this could present unexpected trouble for creatingother vaccines for sexually transmitted diseases, such as AIDS.
More Testing Probably Required
The results were not the clear home run that the vaccine’sdeveloper, SmithKline Beecham, had hoped when it began designingthe latest studies a decade ago. Further testing will almostcertainly be required for the drug to be approved, assuming thatthe company keeps working on the product.
Nevertheless, doctors say a vaccine that offers even partialprotection against a chronic disease is noteworthy. The only othersexually transmitted disease that can be stopped with a vaccine ishepatitis B.
“I would say the chances are good but not at all certain” thatthe herpes vaccine will eventually be approved for routine use,said Dr. Spotswood Spruance of the University of Utah, one of thosewho tested it.
He predicted the vaccine would be given to adolescent girls.Widespread use of the vaccine this way would probably reducegenital herpes for both sexes, since it would lower the chance ofmen coming in contact with infected females.
Herpes Lasts a Lifetime
Genital herpes and cold sores result from closely related bugs.Herpes simplex virus type 1, or HSV-1, causes fever blisters on themouth, while HSV-2 triggers sores on the genitals. Once acquired,both infections last a lifetime.
Both infections grow more common with age. Recent surveyssuggest that in the United States, 45 million people ages 12 andolder are infected with the genital herpes virus.
Spruance and colleagues reported the results of two majorstudies of the vaccine at a meeting in Toronto of the AmericanSociety for Microbiology. Both were conducted on couples in whichone partner had genital herpes but the other did not. The studiesinvolved more than 2,700 people in the United States, Canada,Australia, Italy and New Zealand.
In one of the studies, the partners who were free of genitalherpes had never been infected with either HSV-1 nor HSV-2, whilethe other included those who had HSV-1 but not HSV-2.
During 19 months of follow up, it turned out that the vaccinedid nothing to protect men or to protect women who already hadHSV-1. However, it was about 75 percent effective in warding ofgenital herpes sores in women who had never had either form of thevirus.
About 3 percent got genital herpes after taking the vaccine,compared with about 11 percent of those receiving dummy shots.Another 3 percent of those getting the vaccine became infected butnever developed genital sores.
The researchers said that being infected with HSV-1 probablyhelps protect people from getting genital herpes, and the vaccinedoes little to increase this natural barrier.
Why Only Women?
Why the vaccine works in women but not men is unclear, althoughthe researchers said it probably has something to do withdifferences in sexual anatomy. Perhaps the vaccine boosts theimmune system so it can attack the herpes virus while still in thevagina, but it is unable to stop the virus after it gains access tothe bloodstream through tiny tears in the penis.
“The results are not exactly what we expected,” said GaryDubin, who heads adolescent vaccine development for SmithKlineBeecham in Belgium. He said the company is getting reaction fromregulators and public health officials before deciding what to donext.
However, Spruance said the vaccine could be targeted at girlsages 10 to 13. At this age, he said, about half have not beeninfected with either form of the herpes virus and so could benefitfrom the vaccine.
Despite its drawbacks, the vaccine “really looks veryeffective. It seems potentially useful,” commented Dr. WilliamCraig of the University of Wisconsin, head of the conferenceprogram committee.
The vaccine is made from a protein taken from the outer surfaceof the herpes virus. It is combined with a bacterial toxin thatacts as an immune system booster.