A great deal of research is currently ongoing in Alzheimer's Disease with several different targets that are being pursued. The work that I've been talking about with the vaccine focuses on one of these large areas that involves reducing plaque in the brain as the culprit in Alzheimer's Disease. But several other viable approaches are also being pursued. Another general area are drugs aimed at boosting neurotransmitter levels, still another area is looking at the effect of steroids or hormones such as estrogen or anti-inflammatory compounds. Hopefully some or all of these might eventually be shown to show benefit.
Vitamin E is yet another compound that falls into a class of drugs called anti-oxidants.
There has been one study using Vitamin E, one large clinical study, that showed by some measures but not by other measures that patients had some improvement who were using it. Because the results were mixed, it remains unclear whether it is useful. There's nothing that has been identified with certainly that will delay onset. They also suggest you reduce the likelihood of acquiring Alzheimer's Disease. However, one can do genetic analyses that show that what you inherit from your parents is far more important than where you live or what you've done.