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.

Dave Morgan, an Alzheimer’s researcher at the University of South Florida, said other groups also have worked on ways to refine the vaccine.

The vaccine is meant to clear away tangles of amyloid-beta protein, called plaques, that accumulate in the brains of Alzheimer’s victims.

In earlier tests on mice, the vaccine produced antibodies directed against the AB proteins that cleared the plaques and reversed symptoms of brain degeneration.

The problem, Morgan said, is that it is not clear why the patients in the now-halted trial developed brain inflammation whether immune cells entered the brain to attack the vaccine, or the vaccine provoked a reaction in the brain itself.

“Before we put any more vaccines in people, we need to know what the problem was,” said Morgan, who is not part of the Toronto research team.