Attorney General Maura Healey and Massachusetts General Hospital warned that smoking and vaping may increase the risk of severe illness from COVID-19, in an advisory sent Thursday to medical professionals, educators, and parent and advocacy groups.

Healey and Mass. General assert that smoking and vaping damage the lungs and weaken the immune system, putting people at greater risk of needing hospitalization and advanced life support if they become infected.

“We know smoking and vaping may put people at higher risk,’’ Healey said. “We wanted to get the word out and to make sure people understood that.’’

The advisory was quickly denounced as a political stunt by a pro-vaping advocacy group, which pointed out the lack of studies connecting vaping with COVID-19 illness and cited Healey’s ongoing legal battle with JUUL, the largest e-cigarette maker.

But several experts agreed that now is a good time to urge people to quit both smoking and vaping.

Healey is “sending a message out that could potentially have a far greater positive impact than normal, because we’re all worried about what we can do to make sure we have as healthy lungs as possible,’’ said Matthew L. Myers, president of the Campaign for Tobacco-Free Kids.

There is, in fact, no data showing whether vaping — either tobacco or cannabis — increases the severity of COVID-19, because no one has gathered the information.

But research shows that smokers are more likely to need intensive care or to die if they become infected with the novel coronavirus. And a bread-crumb trail of studies about vaping’s effects on the lungs lead to the notion that vaping could make people vulnerable.

“This is just plain common sense at this time to get off of these products,’’ said Dr. Jonathan Winickoff, director of pediatric research at the Massachusetts General Hospital Tobacco Research and Treatment Center.

In both vaping and smoking, Winickoff said, tiny particles enter the lungs and paralyze the cilia, the hair-like protrusions on cells that clear the lungs of mucus before viruses and bacteria can attach. This makes a person more vulnerable to infections. Additionally, he said, other research shows that e-cigarettes impair the immune system and that the flavoring agents increase inflammation, which makes it harder for lungs to oxygenate the blood.

Vaping cannabis can also damage lung cells and, in animals, smoking marijuana has been shown to increase viral replication, Winickoff said.

“Clean air is what the lungs should be inhaling, especially during a global pandemic," he said.

Winickoff also pointed out that the hand-to-mouth contact common during smoking and vaping could lead to faster spread of the coronavirus.

For Healey, the advisory continues a long history of anti-vaping efforts, which include suing JUUL Labs for marketing their products to young people and suing eight online retailers for illegally selling to Massachusetts consumers.

The renewed concern over vaping comes exactly four months after Governor Charlie Baker’s ban on e-cigarette sales ended. Baker had imposed the ban amid a nationwide surge in lung illnesses related to vaping, mostly the use of illicit cannabis products with toxic additives.

The anti-vaping message Thursday was denounced as “shameful’’ by Gregory Conley, president of the American Vaping Association, a group that works to encourage adult smokers to switch to vaping and that receives funding from e-cigarette retailers.

“Adult smokers should not be scared off from switching to smoke-free nicotine products by unscrupulous politicians out to generate headlines,’’ Conley said in a statement.

The Vapor Technology Association, an industry trade group, raised similar objections in a statement, calling it “reckless’’ to suggest a link between COVID-19 and vaping. “The more public officials discourage Americans from vaping, the more they are encouraging smoking at the worst possible time and without a scientific basis for doing so,’’ the statement said.

Dr. Michael B. Siegel, a Boston University tobacco researcher who supports vaping as an alternative to smoking, nevertheless welcomed Healey’s initiative — cautioning that quitting vaping “should not come at the expense of going back to smoking. Many vapers are former smokers.’’

And the effects of smoking, he said, are clearly more severe, especially in suppressing the immune system. “With vaping, we’re not talking about a very specific effect. It’s a general irritant effect which may make it more difficult to deal with severe lung illness,’’ he said.

“This is a perfect time to really emphasize the risk of smoking and the use of any tobacco product,’’ Siegel said.

With children sequestered at home, many parents are learning for the first time that their children are vaping, either because they discover vaping products or because their children go into nicotine withdrawal, said Dorian Fuhrman, a cofounder of PAVe — Parents Against Vaping e-cigarettes.

Fuhrman said her New York-based advocacy group has been receiving distress calls from many families. A mother who had been active in PAVe was shocked to see a disposable vaping pod fall out of her teenage son’s pocket. Another wrote that her daughter and husband, terrified of COVID-19, had both decided to quit, and after one day they were “melting down.’’ Fuhrman pointed them to resources to help cope.

Andy Tan, assistant professor of social and behavioral sciences at the Harvard T.H. Chan School of Public Health, noted that smoking rates are highest among low-income and marginalized populations, the same people who are facing the most stress, such as job loss, amid the pandemic.

Urging people to quit an addictive substance in the midst of such troubles “is asking a lot,’’ he said. But he said many of these people are vulnerable to COVID-19 in other ways, and it would be to their advantage to remove the risk that comes with tobacco use.

Healey’s advisory includes suggestions on how to quit, such as obtaining nicotine patches or gum, seeking coaching and support, and contacting the National Quit Line: 1-800-QUIT-NOW.

Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her on Twitter @felicejfreyer