VIENNA - A new vaccine against Alzheimer's, developed by the Austrian biotechnology firm Affiris, will soon be tested in six European countries, the company announced Friday.

Some 420 patients will be recruited to take part in clinical trials in Austria, Croatia, Czech Republic, France, Germany and Slovakia, Affiris said in a statement.

The AD02 vaccine, developed with British drugmaker GlaxoSmithKline, was already tested for safety and tolerability over the past year.

The clinical trials will now test its efficacy, with results expected as early as 2012, the company said.

ADO2 is meant to prevent the building up of beta-amyloid plaques in the brain, which cause the degradation of nerve cells and are believed to play a crucial role in causing Alzheimer's disease.

The vaccine works by causing the body to attack these plaques by producing more antibodies, Till Jelitto, a spokesman for Affiris, told AFP.

More specifically, these antibodies are meant to attack only the part of the beta-amyloid protein that causes the plaques, he added.

This would reduce the risk for patients, as the protein as a whole already exists in healthy individuals.

The current vaccine is therapeutic, meaning it is aimed at treating patients already affected by the disease. But if results are positive, the technology could also be used to manufacture a prophylactic, or preventative, vaccine, Jelitto said.

In 2001, tests for a first vaccine against Alzheimer's disease were conducted in the United States and Europe but had to be cut short after serious side effects emerged.

Another vaccine was tested in Sweden in 2005.

Alzheimer's disease, also known as AD, is a neuro-degenerative disease that affects cognitive functions, further impacting patients' behaviour and social adaptation.

The disease, which still has no known cure, affects about six million people in Europe every year.

Affiris is also working on vaccines against Parkinson's and atherosclerosis.