Scientists have developed a nasal Alzheimer's disease vaccine that they believe could be key to preventing and treating the degenerative cognitive condition in humans.

The vaccine, which blocks a protein believed to cause the disease from accumulating in the brain, greatly reduced atrophied brain matter in mice with the disease.

The team behind the vaccine, whose members include researchers from Kyoto University, said its experiments with the mice showed the vaccine reduced changes in the brain and abnormal behavior brought on by the disease.

The scientists announced their findings in the online version of British science journal Nature on March 24.

"Much more research is necessary for the vaccine to be used in humans, but it is an accomplishment that can contribute to the development of a dementia cure," said team member Haruhisa Inoue, a professor at Kyoto University.

Certain types of dementia, including Alzheimer's disease, are characterized by an abnormal accumulation of "tau" proteins in the brain.

Drugs are available that improve Alzheimer's symptoms, but finding a cure for the disease has proved elusive.

Japan has about 3 million patients of Alzheimer's and similar diseases, according to the team.

In the experiment that used mechanisms of the immune system, the team incorporated a gene into a harmless virus to make it produce tau and administered it nasally to mice with genes prone to developing dementia.

The vaccine appeared to stimulate the immune systems of the mice, as their antibodies, which react with tau and remove protein, more than doubled compared to when no measures were taken.

In the cases of vaccinated mice, the brain’s areas atrophied by dementia were only two-thirds of those of mice that weren’t vaccinated. As a result, the vaccinated mice exhibited behavior close to healthy ones, the team said.

The vaccinated mice also displayed no side effects during the eight months the scientists observed them.

Readers can view the team's research article at: (https://www.nature.com/articles/s41541-020-0172-y)