Trials of a vaccine that might slow or reverse the progress of Alzheimer's disease have been halted after 12 volunteer patients became seriously ill.
The tests, conducted in five countries, including Britain, involved 360 people and started last autumn after initial safety trials had not indicated any problems.
But trouble emerged last month when four patients in France developed inflammation in their brains and central nervous systems. The trials were temporarily suspended but further checks have revealed eight more cases, although it was not clear where.
Experts in the so-far irreversible brain condition are still hoping the problems will not deal a death blow to promising research in tackling the disease which affects 400,000 Britons.
The volunteers, all of whom had mild to moderate Alzheimer's, displayed symptoms ranging from fever, headache and vomiting to muscle weakness and seizures.
The vaccine, known as AN-1792, is being developed by the Irish-based pharmaceutical company Elan, in partnership with American company Wyeth-Ayerst Laboratories. The human trials were launched after tests on genetically modified mice had successfully removed clumps of beta amyloid, the protein concentrations closely associated with Alzheimer's.
Safety tests were conducted on volunteers in the US and Britain. Those in America ensured there were no side effects to a single dose, while those here involved patients being injected four times over six months. The hope was then that further trials lasting up to two years would justify optimism that the disease could be first slowed and later prevented in at-risk patients.
No one was available at Elan last night but a spokesman told the Washington Post yesterday that those who had suffered reactions were responding "appropriately" to treatment.
Richard Harvey, research director of the Alzheimer's Society, said: "Trials have not been completely abandoned. The company has decided not to give people any more vaccine. A large number of people have been vaccinated and they are being followed up. They may be able to draw some conclusions from that.
"This still looks a very good strategy for treating Alzheimer's. It may be something about the vaccine or a component. It may be something about the patients."
