The American Medical Association on Monday urged Americans to stop using electronic cigarettes of any sort until scientists have a better handle on the cause of 450 lung illnesses and at least five deaths related to the use of the products.
The AMA, one of the nation's most influential physician groups, also called on doctors to inform patients about the dangers of e-cigarettes, including toxins and carcinogens, and swiftly report any suspected cases of lung illness associated with e-cigarette use to their state or local health department.
The recommendation followed advice from the US Centres for Disease Control and Prevention on Friday for people to consider not using e-cigarette products while it investigates the cause of the spate of severe lung illnesses associated with vaping.
Many, but not all, of the cases have involved those who used the devices to vaporize oils containing tetrahydrocannabinol (THC), the psychoactive component of cannabis.
CDC officials said some laboratories have identified vitamin E acetate in product samples and are investigating that as a possible cause of the illnesses.
Public health experts have not found any evidence of infectious diseases and believe the lung illnesses are probably associated with a chemical exposure.
Megan Constantino, 36, from St. Petersburg, Florida, quit vaping six days ago after hearing reports of the illnesses and deaths related to vaping.
"It scared me into quitting," she said.
Like many users of vaping pens, Constantino picked up the device after quitting cigarette smoking three years ago, and said, "It's the hardest thing I've ever done."
She added, "I threw the last cartridge away. I took a picture of it and I literally cried."
Constantino said many people who vape have been "on pins and needles" for the investigation results, and she is concerned that the reports of a link to vaping THC may give people an excuse to ignore the warnings.
E-cigarettes are generally thought to be safer than traditional cigarettes, which kill up to half of all lifetime users, the World Health Organisation says. But the long-term health effects of vaping are largely unknown.
The US Food and Drug Administration has faced mounting pressure to curb a huge spike in teenage use of e-cigarettes, a trend that coincided with the rising popularity of Juul e-cigarettes.
"We must not stand by while e-cigarettes continue to go unregulated. We urge the FDA to speed up the regulation of e-cigarettes and remove all unregulated products from the market," AMA president Dr. Patrice Harris, said in a statement.
Gregory Conley, president of the American Vaping Association, which advocates for cigarette smokers to switch to nicotine-based vaping devices, said the AMA should be "ashamed of themselves for playing politics with people's health and protecting the profits of drug dealers."
He criticised the AMA for "fearmongering about nicotine vaping products" while not mentioning "the very real risks of vaping illicit THC products."
Juul Labs declined to comment. Altria Group Inc owns a 35 per cent stake in Juul.