A vaccine to help kick the habit is being tested on smokers.

The American Cancer Society said 46 million adults smoke. Another 8.6 million Americans are living with a serious illness caused by smoking. While there are many ways to quit smoking, most people will relapse. Now, doctors may have found a vaccine to help smokers stop for good.

Wayne Thompson has been lighting up for 35 years, but with two new grandchildren on the way, he says he's ready to quit.

"With the grandbabies coming, I don't want to be subjecting them to secondhand smoke," he said.

Thompson enrolled in a study on a vaccine called NicVax that could help him quit. It's one of a few smoking vaccines to make it to human trials. For the study, Thompson gets eight shots and answers questions about his experience.

"Did it reduce your hunger for food? Did it make you nauseous? Did it make you less irritable?" Thompson said.

Dr. Dorothy Hatsukami said the vaccine stimulates the immune system to make antibodies that stop nicotine it its tracks.

"These antibodies actually attach themselves to the nicotine molecules and this complex is so large it can't pass through the blood-brain barrier, and so this nicotine cannot get into the brain," Hatsukami said.

Since nicotine cannot reach the brain, smokers do not experience its pleasurable effects.

The goal is to make smokers lose interest in smoking.

"So, it just becomes like smoking a cigarette that has no nicotine in it," Hatsukami said.

Some smokers in the study will receive the vaccine, while others will get a placebo.

Thompson said he has not yet noticed a difference, but he believes the vaccine is a step in the right direction. Still, he knows the decision to quit is up to him.

"You've got to make the determination yourself. You've got to say, 'I am going to do it,'" he said.

Doctors hope the study will help them find the most effective dose of the vaccine and how often smokers need it. Preliminary studies show it is safe in humans, but doctors want more tests.

Trials are under way at the University of Minnesota, the University of Nebraska and the University of Wisconsin.

For more information, contact Ashley Burt, with the University of Minnesota Academic Health Center at (612) 624-2449.