"The results of this study represent a promising step toward an effective medical treatment for cocaine addiction," said Nora Volkow, director of NIDA, in a statement. "Provided that larger follow-up studies confirm its safety and efficacy, this vaccine would offer a valuable new approach to treating cocaine addiction." NIDA, a department of the National Institute of Health, is the primary Federal agency for conducting and supporting medical research on drug abuse.

A larger study is planned for January, and researchers hope similar vaccines could work for other addictive drugs such as heroin, nicotine, and methamphetamines, although not for alcohol or marijuana, according to The Los Angeles Times.

Like other vaccines, the anti-cocaine vaccine stimulates the immune system to produce antibodies that attach themselves to cocaine molecules in the blood, blocking them from reaching the brain and inhibiting the drug's euphoric, energetic effects, rather than destroying or deactivating the disease-causing agents, as antibodies normally do. Researchers found that 53 percent of patients who attained a high level of the antibodies -- at least 43 micrograms of antibodies per ml of urine -- showed at least a 50 percent reduction in cocaine use, compared with 23 percent among users who attained a low level of the antibodies.

Cocaine-free urine tests were also achieved 45 percent of the times at those with high antibodies, compared with 35 percent for those who got placebo or who didn't form as many antibodies. But only 38 percent achieved the desired level of antibodies, and they had only two months of adequate cocaine blockade, indicating that they will likely need more shots. Researchers concluded they need improved vaccines and boosters.

Health problems associated with cocaine include heart attacks, respiratory failure, strokes, seizures, violent behavior, and death. One in three emergency department visits for drug- related illness is due to cocaine dependence. The Justice Department estimated the annual cost of drug abuse on the U.S. economy in 2002 at nearly $181 billion.

The vaccine's most frequently reported side effects were tenderness and hardness at the injection site, feeling cold, hot flashes, nausea, and increased sweating.

The subjects of this study did not achieve complete abstinence from cocaine, but "a reduction in use is associated with a significant improvement in cocaine abusers' social functioning and thus is therapeutically meaningful," a leader of the research, Thomas Kosten, told Bloomberg News. "If a real vaccine-maker wanted to do this, it could be on the market in two years."

In 2005, drug maker Xenova showed in Phase I clinical trials that almost half of those given its TA-CD cocaine vaccine stayed off the drug for six months. Xenova owner Celtic Pharma helped support the new study, but it's curious that no other major pharmaceutical company has picked this up as the number of addicts is large enough to make it commercially viable. With any luck, the U.S. will help fund a vaccine that could cut down such high social costs to the economy.