Battling a cocaine addiction is much tougher than researchers initially thought. This is exemplified in the research of a widely reported experimental vaccine which is used to counteract coke addiction. The vaccine showed strong results at first, but lost its effectiveness after a few months.

The vaccine works by increasing antibodies that bind to cocaine, which stops the high. The vaccine was tested on 94 adults selected from methadone maintenance programs, who also received behavioral therapy. Thirty-eight percent of participants developed enough antibodies to repress their cocaine use. However, after two months the effect tapered off.

Jeffrey T. Parsons, professor and chair of psychology at Hunter College, said "The results are promising, to be sure, but still the majority of participants did not respond."

The study's results were published in the October issue of the Archives of General Psychiatry. Cocaine addiction affects 2.5 million people national, and of that only 809,000 are being treated.