WASHINGTON -- Modifications to an experimental vaccine for Alzheimer's disease that was discontinued because of side effects might make it safe, a study suggests.

Researchers in Canada and Germany found that a more refined form of the vaccine worked in mice, which raised the chance that it might not produce in humans the inflammation that ended clinical trials.

That remains only a possibility and requires more research, said JoAnne McLaurin of the Centre for Research in Neurodegenerative Diseases at the University of Toronto. She is the first author of the study being published Tuesday in the online edition of the journal Nature Medicine.

In January, the Irish drug company Elan Corp. suspended a 360-patient experiment with the vaccine after 15 patients suffered serious brain inflammation.

Elan announced in March it was abandoning the vaccine, although the company said it plans to continue exploring ways to slow the worsening of Alzheimer's.