WASHINGTON (Reuters) – GlaxoSmithKline said on Thursday that it was stopping development of a genital herpes vaccine after it failed to protect women against the virus.
The U.S. National Institutes of Health said the test of 8,000 women in the United States and Canada showed the Simplirix vaccine failed to protect them significantly from genital herpes.
"The estimate of vaccine effectiveness was 20 percent, but all estimates have statistical uncertainty, and this effect was not substantially different from zero," the National Institute of Allergy and Infectious Diseases, an NIH institute, said in a statement.
The Phase III trial, the last step before regulatory approval of a drug or vaccine, was sponsored by Glaxo at 50 sites in the United States and Canada.
"GlaxoSmithKline has made the decision not to pursue further worldwide development of Simplirix," the company said in a statement.
The women, aged 18 to 30, all started out free of infection by either the herpes simplex 1 virus that causes cold sores or the related HSV-2, which causes genital herpes.
The researchers sponsored by the NIAID followed the women for nearly two years to see if they became infected with either virus in their day-to-day lives.
It had been a difficult trial to put together because both viruses are very common.
Between 50 percent and 80 percent of Americans are infected with HSV-1, which usually causes cold sores. Up to 20 percent of those over 12 are infected with HSV-2, and more than 1 million new cases of genital herpes are diagnosed in the United States each year.
Genital herpes is sexually transmitted and can not only cause painful and debilitating outbreaks of blisters, but it can also kill newborns if passed on by the mother in childbirth.
The 8,000 volunteers had been divided into two groups. Half got the vaccine against herpes, which included an immune system booster called an adjuvant.
The other half got Glaxo's hepatitis A vaccine instead.
Earlier studies had shown the herpes vaccine protected 70 percent of women whose sex partners were infected with the virus.
It did not protect men at the time -- something that puzzled the researchers -- and the NIH said it did not know why the vaccine did not work this time in women, either.
More details are available at http://www.niaid.nih.gov/news/newsreleases/2010/Pages/Herpevac.aspx.
Vaccine experts estimate it can take up to $1 billion to develop a new vaccine. Some are easy -- the first smallpox vaccine was invented in 1796.
But others are far more difficult, and viruses such as herpes and HIV, which take up permanent residence in the body, have proved impossible to eradicate or vaccinate against.
Researchers are also struggling to make vaccines against the malaria parasite.