Multiple sclerosis (MS) could be prevented with a vaccine normally used to immunise against tuberculosis, an Italian study suggests.
Researchers at the Sapienza University of Rome believe early signs of the condition can be fended off using a vaccine known as Bacillus Calmette-Guerin (BCG).
The MS Society has hailed the study as a major leap forward, but said further trials need to be carried out.
MS is condition which causes problems with vision, balance and movement due to the body's own immune system attacking the myelin coating on nerves in the brain and spinal cord.
Early symptoms involve people experiencing blurred vision and numbness.
The team in Rome gave BCG to 33 people who had exhibited such signs and then monitored their health over a period of five years.
Some 40 people were also given placebo so accurate comparisons could be made.
At the end of the study period, 58 per cent of those given the vaccine were found to have not developed MS compared to just 30 per cent of those given the dummy drug.
Writing in the Neurology journal, study leader Dr Giovanni Ristori said: "These results are promising, but much more research needs to be done to learn more about the safety and long-term effects of this live vaccine.
"Doctors should not start using this vaccine to treat MS or clinically isolated syndrome."
Dr Susan Kohlhass, head of biomedical research for the MS Society, has called for larger scale studies to be carried out to test the findings further.
In September, a study from the University of Dundee found that diagnosis of the condition is failing in the UK and people with it are living for longer.
The team found that in the 20 years up to 2010 the number of people diagnosed with MS fell by an average of three per cent each year.
However, the number of patients managing the disorder rose by 2.4 per cent thanks to improved mortality rates.