A new vaccine designed to prevent people with genital herpes from passing the virus on to their sexual partners has begun its first patient trials at a London hospital. Two healthy volunteers have been given the jab at the Chelsea and Westminster Hospital, in the first phase of a study that could eventually provide the first effective immunisation against the incurable sexually transmitted infection.

The safety trial, which will eventually involve 42 people, comes after encouraging results in animal models which suggested that the vaccine has a good prospect of succeeding where other candidates have failed.

Scientists behind the study said that if the trials proceed successfully, a vaccine could be ready for widespread use in about five years. Jabs would initially be offered to the sexual partners of people who carry genital herpes to protect them from infection, though wider immunisation is also a possibility. One in ten adults carries herpes simplex virus 2 (HSV2), which causes genital herpes, though most do not know they are infected as they have few or no symptoms. It often lies dormant for long periods, causing intermittent episodes of painful sores.

It is highly contagious when sores are present, and while condoms and antiviral drugs reduce the risk they do not eliminate transmission. The drugs can control symptoms, but do not clear the virus from the body.

While candidate vaccines have been developed before, they have failed to produce good protection because of HSV2’s ability to hide from the body’s immune system. BioVex, a biotechnology company, has designed the new ImmunoVex HSV2 vaccine to counter this problem. It is based on a live but weakened version of HSV2, which has been engineered to silence four genes that help the virus to hide from the immune system. This should allow it to generate an immune response capable of preventing infection.

Robert Coffin, chief executive of BioVex, said: “We have based our design on the failures of the past, and we hope this will make our vaccine more likely to succeed.” In pre-clinical research Immunovex vaccine has prevented the development of any symptoms when animals are deliberately exposed to HSV2, which improves on previous vaccine candidates.

Simon Barton, a consultant in genito-urinary medicine at Chelsea and Westminster Hospital, who is running the study, said that a genital herpes vaccine would have important benefits. “For many of the people with genital herpes I look after, the big issue is having a way of protecting their partners,” he said. “They can reduce the risk of transmission by using condoms and taking antiviral drugs every day, but these are far from ideal and they do not reduce the risk to zero.”

The initial phase one trial will evaluate whether the virus is safe in healthy volunteers, and whether it generates a good immune response. If the results are positive, it will go on to be tested for efficacy on the partners of people with herpes.

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