A team of Japanese reseachers plans to use monkeys for testing the effectiveness of a vaccine against the H5N1 strain of the bird flu virus.

Researchers from Hokkaido University and the Shiga University of Medical Science will carry out the tests on long-tailed macaques, also known as crab-eating monkeys, Kyodo News reported Saturday.

The results are expected within about six months.

The experiment could shed light on aspects of the infection mechanism of the viral strain that remain a mystery, and pave the way for a human vaccine, the researchers said.

"The highly virulent H5N1 strain virus could kill mice and chickens when they were infected with it but it remains unknown what exactly would happen for monkeys," Kazumasa Ogasawara, a Shiga professor, told Kyodo.

"Monkeys have immune system cells akin to those of humans, so the research should also be useful in devising measures against infection in humans," he said.

The researchers had so far given the vaccine to seven monkeys, and six of them have developed a type of antibody that appears to have removed the virus from their bodies, Kyodo said.

In the planned test, the researchers will infect those six as well as three non-vaccinated monkeys to check what symptoms appear.