Viewpoint: Yes, current claims for an Alzheimer's vaccine properly take into account the many defects that the disease causes in the brain—the claims are based on sound experimental results regarding beta-amyloid plaques.

Viewpoint: No, a vaccine based on preventing the formation of beta-amyloid plaques is premature and could well prove ineffective—and possibly even harmful to humans.

By the end of the twentieth century, Alzheimer's disease, a condition once considered very rare, had emerged as the most common cause of dementia. Alzheimer's disease affects approximately four million people in the United States alone. Although almost half of all patients with dementia appear to...