Researchers have begun an early clinical trial of a new vaccine for Alzheimer's disease.
Alzheimer's slowly destroys a person's memory and thinking skills.
Scientists believe a harmful brain protein called tau plays a big role in the disease.
The vaccine is designed to help the body clear this tau protein away.
This first trial mainly tests whether the vaccine is safe in people over about a year.
Because it is early-stage work, doctors are careful not to promise a cure yet.
Even so, the trial is part of a large rise in Alzheimer's research and offers real hope.