"For people who have a desire to stop using, the vaccine should be very useful," said Dr Tom Kosten, professor of psychiatry at Baylor College of Medicine in Houston, Texas.

"At some point, most users will give in to temptation and relapse, but those for whom the vaccine is effective won't get high and will lose interest."

Dr Kosten is collaborating with his wife Therese, a psychologist and neuroscientist also working at Baylor College, on the new vaccine in an effort to help cocaine addicts.

The new vaccine trains the human immune system to attack cocaine molecules as if they were a threat.

Cocaine molecules are generally believed to be too small to be detected by the immune system.

The Kostens have found a way around this by combining cocaine that has been treated to make it non-euphoric with deactivated cholera proteins.

The body reacts to the combination, but then also recognises pure cocaine as a threat and begins making antibodies.

These antibodies bind themselves to the cocaine molecules, preventing them from reaching the brain and then causing the euphoria that can lead to addiction.

"It's a very clever idea," says David Eagleman, a neuroscientist at Baylor College.

"Scientists have spent the last few decades figuring out reward pathways in the brain and how drugs like cocaine hijack the system."

"It turns out those pathways are difficult to rewire once they've seen the drug."

"But the vaccine just circumvents all that."

The Kostens have now made a formal request to the US Food and Drug Administration for wide-ranging human trials to test the vaccine's efficacy.

But one expert in the field sounded a note of caution.

"Addiction vaccines are a promising advance, but it's unlikely any treatment in this field will work for everyone," said Dr David Gorelick, a senior investigator at the National Institute on Drug Abuse.

"Still, if they prove successful, they will give those working in drug addiction an important option."