The herpes simplex 2 virus (HSV2) is spread by vaginal, anal or oral sex.
People remain infected for life, as some of the HSV2 viruses hide away in nerve cells where they lie dormant.
Most people never realise they are infected but others suffer from outbreaks of painful symptoms, including genital lesions.
The virus can also cause complications such as meningitis, and is occasionally passed on to babies during birth with fatal results.
But an experimental vaccine developed by Harvey Friedman at the University of Pennsylvania has prevented genital lesions in all mice and guinea pigs tested.
In 98 per cent of mice and 80 per cent of guinea pigs it also prevented the low-level “hidden” infections.
Friedman’s team is now testing whether the vaccine can also protect against herpes simplex 1, or the cold sore virus. »