This research study is studying an investigational vaccine (AV-1959D) in individuals who have Mild Cognitive Impairment (MCI) or who have early on set Alzheimer's disease. AV-1959D is a new experiemental vaccine being developed for treatment of Alzheimer's disease. Vaccinnes are biological preparations that stimulates the human body's own protective mechanisms to prevent or treat diseases. In this study participants will either receive the vaccine or a placebo (an inactive substance that looks like the study drug). Participants will be asked to attend a screening vist to ensure you are eligible to participate. If eligible you will be asked to attend 8 additional visits to the clinic over the course of about 70 weeks. Participants who are eligible to participate will receive up to three vaccines through a needleless delivery system.
Criteria:60-85 years old.
Be Diagnosed with Mild Cognitive Impairment or Alzheimer's Disease, early on-set.
Have no Uncomtrolled Medical Conditions.
Have a Study Partner willing to attend all study visits with you.