Researchers at the University of Wisconsin at Madison have begun recruiting for human trials of a possible vaccine that could prevent nicotine addiction, the Associated Press reported June 21.

Forty volunteers are being sought to test the vaccine, which blocks nicotine receptors in the brain. The test subjects will get stop-smoking counseling and then make twice-monthly visits for a year to a clinic, where they will receive either the vaccine or a placebo.

A previous study showed the vaccine to be safe; this one will measure its efficacy.