Scientists desperately seeking a cure for Alzheimer's disease received distressing news this week when it was announced that a once-promising vaccine may induce strokes. Designed to "recognize" and attack the build-up of amyloid beta, a substance believed to be characteristic of the neurological disorder, the vaccine was still in the testing process as researchers used lab mice manipulated to develop the major symptoms of Alzheimer's disease. But a new study, appearing in Friday's issue of the journal Science, reveals that during testing, the test mice had twice the number of cerebral hemorrhages as those that did not receive the vaccine. The Swiss, German and American researchers also discovered the incidence of severe blood clots.

Earlier this year, pharmaceutical maker Elan Corporation permanently halted the development of a similar experimental Alzheimer's vaccine, AN-1792. Clinical trials of the amyloid beta drug were suspended after four patients in France developed inflammation of the central nervous system (CNS). Researchers decided to permanently halt the vaccine's development after a dozen more users suffered adverse side effects.