Scientists at Oxford University are one step closer to developing a vaccine for the killer virus meningitis B.

Researchers have found out what changes the harmless meningicoccus microbe into one which invades the bloodstream and fights the human immune system. It can kill within hours.

Now they hope they will be able to use the information to develop a vaccine against meningitis B, which could be ready by next year.

The microbe is usually harmless and lives at the back of people's noses and throats. But when 75 special genes are activated, it can become lethal. Although there is a vaccine for meningitis C, which accounts for 40 per cent of cases in the UK, there is no similar immunisation for the B strain - which causes other meningitis illness.