A Canadian smoking cessation doctor says vaping as a way to quit smoking doesn't seem to work, and most adults continue to smoke and vape — a concerning finding that comes amid the skyrocketing popularity of e-cigarettes among young people.

"The indications are perhaps 15 to 20 per cent of people may be able to quit using vaping but about 60 to 70 per cent of people continue to smoke and vape at the same time, as opposed to converting to vaping altogether," said Dr. Robert Reid, of the Ottawa Heart Institute, who works at a large smoking cessation program.

His observations build on the findings of a randomized trial on e-cigarettes and nicotine-replacement therapy. The trial published in the New England Journal of Medicine in February looked at users in the United Kingdom, where the strength of nicotine in e-cigarettes are restricted to no more than 20 milligrams per millilitre. Currently, Health Canada's maximum limit is three times higher.

Reid said the findings on dual users — people who continue to smoke cigarettes and vape — reflected the addictive properties of e-cigarettes. After a year, only about three per cent of those assigned to the nicotine patch group were still using the patch, but about 45 per cent in the vaping group continued to vape.

At the Canadian Stroke Congress this week in Ottawa, Reid warned that many of the newer vaping products deliver as much nicotine as cigarettes. He also flagged how flavouring agents may also cause damage to blood vessels.

"This explosion of cases in the U.S. has us questioning 'Is this a safer alternative?'" Reid said.

Newer generation e-cigarette devices with pods are engineered to deliver much higher doses of nicotine in the body more rapidly, he said.

"Once it started to be commercialized … there's evidence from the experience in the U.S. that there was a deliberate attempt to make this appeal to younger users, specifically through using state-of-the-art social media techniques to engage people and also using social influencers very dramatically to change its trajectory of adoption by young people," Reid said.

On Thursday, the U.S. Federal Trade Commission ordered several e-cigarette companies to turn over sales and advertising data, a sign of a likely probe of company marketing practices.

As of Oct. 1, the U.S. Centers for Disease Control and Prevention (CDC) reported 1,080 cases of serious illness resembling inhalation injury linked to e-cigarettes and vaping, as well as 18 deaths. The cases increased 275 in a week.

"We are concerned that risky product is still available, and that's one of the reasons that we have intensified our recommendations or warnings," Dr. Anne Schuchat, principal deputy director of the CDC, told reporters. "We haven't seen a measurable drop-off in the occurrence of new cases and so we don't feel that either individuals have changed their behaviour or the products are gone."

So far, about 70 per cent of the U.S. patients were male, 80 per cent under 35 years old and 16 per cent younger than 18, Schuchat said.

Most patients reported a history of using products containing tetrahydrocannabinol or THC, the cannabis ingredient that gives a high.

Last week, doctors in Illinois and Wisconsin said most of their cases so far have been in people who got their THC-containing product off the street. Whether that pattern holds across the United States is not known.

Dr. Chris Simpson, a cardiologist and vice-dean (clinical) at Queen's University, said Friday at the Canadian Stroke Congress that knowledge of the potential benefits and harms of cannabis is still in its infancy.

Last week, health officials announced a Quebec resident who'd been vaping for a few months to quit smoking was the first confirmed case of the severe vaping-related breathing illness in Canada.

Canadian and U.S. health officials say anyone who has used e-cigarettes or vaping products, and has symptoms such as shortness of breath, cough, chest pain, with or without vomiting, diarrhea, abdominal pain or fever is advised to consult a health-care professional.

The exact cause or causes of the illness remains unknown.

"I think we have the feeling right now that there may be a lot of different nasty things in e-cigarettes or vaping products, and they may cause different harms in the lungs," CDC's Schuchat said.

To quit vaping, Schuchat suggested using approved cessation products, such as nicotine patches and gum together with counselling — not returning to smoking.

With legalization of cannabis in Canada, Reid said data is starting to be collected on the "high proportion" of smoking cessation patients who also use cannabis.