Researchers said that the dependency of addicts on cocaine can be reduced to half by the use of a vaccine.

The vaccine was given to 55 cocaine addicts, by doctors at the Yale University School of Medicine, and it was found that 38 percent of them were able to acquire the required antibody levels. However the researchers say that repeat injections would be needed by the addicts.

Studies done on animals and human studies have shown that high levels of anti-cocaine antibodies in the blood can stop addicts experiencing a high.

A total of 115 cocaine and opiate-dependent individuals were randomly assigned to receive five vaccinations of the active vaccine or five vaccinations of a placebo treatment.

In about three days the cocaine is flushed out of the body so the doctors tested the urine of all the addicts for metabolized cocaine three times a week for 24 weeks.

Among the 55 people who completed the course 21 attained antibody levels of 43 micrograms per milliliter or higher.

Those who were treated with active vaccine showed more improvement in their dependency on cocaine.