This week, two significant announcements were made at the World Alzheimer Congress, a gathering of more than 3,000 experts in Washington, D.C. On July 11, scientists at Elan Pharmaceuticals reported that a vaccine that reverses some of the effects of Alzheimer's has cleared its first test in humans. Since the first observation by Dr. Alois Alzheimer in 1906, researchers have long noted the presence of many beta amyloid plaques in the brain tissue of people who had died from Alzheimer's, though the exact cause of the disease remains unknown. This new vaccine works to clear these plaques out of the brain and prevent them from forming. Provided further clinical trials are successful, Elan hopes to begin mass marketing the vaccine within four to seven years. The day after this announcement, researchers from the New York University School of Medicine reported findings that suggest "memantine, a drug that acts on a key central nervous system receptor, may help slow the progression of moderately severe to severe Alzheimer's disease." This is the first drug developed to date for these patients, who account for about one-third of all Alzheimer's sufferers. Memantine, researchers believe, works on the area of the brain that has to do with thinking and memory. Though currently available in Germany for dementia patients, further testing is required before Memantine can be approved for widespread use in the US.