Scientists have developed an anti-nicotine vaccine that could take the pleasure out of smoking a cigarette.
A single dose of the vaccine was able to protect mice against nicotine addiction for life.
Further tests are needed before starting human trials, which would take several years, but Professor Ronald Crystal of Weill Cornell Medical College in New York said the early signs are good.
He said: "We are very hopeful that this kind of vaccine strategy can finally help the millions of smokers who have tried to stop, exhausting all the methods on the market today, but find their nicotine addiction to be strong enough to overcome these current approaches."
The new vaccine contains a harmless virus that has been engineered to carry the genetic information to make anti-nicotine antibodies. The virus selectively infects liver cells, which then start to make a steady stream of the antibodies.
These hunt down any nicotine molecules in the bloodstream, neutralising them before they reached the brain, preventing a smoker from getting a nicotine hit.
In tests, vaccinated mice who were subsequently given nicotine continued with their normal activity. But mice who had not been given the vaccine "chilled out", say the researchers, a sign that the nicotine had reached their brains.
The experiments are described in the journal Science Translational Medicine.
Previous tobacco vaccines failed because they contained antibodies. The jabs had to be given so frequently to keep antibody levels topped up that they proved expensive and impractical.
But the cost of the new vaccine is likely to be far lower, because it turns liver cells into antibody factories.
Professor Crystal said that if a future human vaccine was completely safe it could be given to children before they were tempted to try a cigarette, preventing nicotine addiction. But more likely it would be used by smokers to quit.
"They will know if they start smoking again, they will receive no pleasure from it due to the nicotine vaccine, and that can help them kick the habit," he said.
British scientists said the results were interesting but warned far more research was needed.
Professor Anthony Dayan, the former head of the Department ogf Health and social Security Toxicology Department at St Bartholomew’s Hospital, said: "Nicotine addiction via smoking is harmful but is it ethical to produce a major and enduring change in someone’s body to prevent it when other less major types of treatment are feasible?
"The clinical testing of this gene therapy would also be extremely difficult, lengthy and costly because of the need to show safety and retained efficacy in man over a very long period, certainly many months or more likely several years.
"Who could support such trials other than government agencies and is it politically and financially conceivable they would attack so directly the popular habit of smoking?"