A clinical trial evaluating the efficacy and safety of Alzheimer's vaccine ACC-001 was suspended in early April because one of the study's participants developed inflammatory brain lesions. The participant was hospitalized but later released.

The vaccine targets beta amyloid, a protein that accumulates in the brains of those with Alzheimer's disease. Interestingly, a previous study evaluating a similar vaccine was discontinued because some participants developed encephalitis -- another type of brain inflammation.

Dr. Jeffrey Cummings of UCLA was not involved in the trial, but he suggested that we shouldn't jump to conclusions about the most recent study because little information is available about the nature of the participant's lesions or whether the person was receiving the vaccine or a placebo. Still, the fact that two different studies of Alzheimer's vaccines have encountered problems with brain inflammation highlights the difficult road ahead for scientists trying to find a safe, effective vaccine against Alzheimer's.

More About Beta Amyloid:

• What Causes Alzheimer's?
• Which Comes First: The Plaque Or The Disease?

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