Early trials of a vaccine which could help people to give up smoking are proving promising, say scientists.
Xenova, the British-based company behind the vaccine, which may also help cocaine addicts, started testing it two years ago.
Many smokers find it difficult to quit
Dr Campbell Bunce, a scientist at the company, told the British Association science festival at Salford University that the vaccine had proved safe and well-tolerated.
It works by stopping nicotine or cocaine from entering the brain.
As a result, these drugs are no longer able to stimulate the reward centres in the brain that cause cravings.
The vaccine prompts the body's immune system to create antibodies which bind nicotine or cocaine in a person's bloodstream, preventing it from travelling into the brain.
It could be given to people who are having problems kicking their smoking or cocaine habit.
In theory, it could also be given to young children to prevent them from taking up these habits in the first place.
"You can imagine it being used by parents of adolescents, who might want their children to be protected against a drug-taking habit," said Dr Bunce.
"That is something with ethical considerations that we would have to consider."
The vaccine has so far proved safe to use on both smokers and cocaine users.
Scientists are now planning to test how effective it is. Trials on cocaine users are expected to start later this month.
However, cocaine users have reported that the immunisation reduced the sense of euphoria they felt after taking the drug.
Dr Bunce said he did not envisage the vaccine stamping out cravings for cigarettes straight away. Nor would it alleviate the withdrawal symptoms associated with giving up smoking, such as anxiety and depression.
But the vaccine could help to ensure that people who quit never take the habit up again.
"Often an ex-smoker will relapse at a party, in a moment of weakness," said Dr Bunce.
"Hopefully, the presence of these antibodies will reduce the hit of the cigarette and that desire for another cigarette will be significantly blunted."
One possible concern, he said, was that people might be tempted to smoke more to get the same "buzz" they were used to. It is not yet known whether this could happen.
A spokesman from the anti-smoking group ASH said it would welcome the introduction of a vaccine to help people kick the habit.
"People who try to give up smoking can find it very difficult," he told BBC News Online.
"A vaccine could help these people or people who have consistently failed to give up.
"But as long as it is safe, it should be seen as an extension of the existing nicotine replacement therapies.
"We would not support vaccinating people to stop them from smoking."