A majority of young e-cigarette users vape Juul products, and the most popular Juul flavor among high schoolers this year was mint, according to a pair of new studies published in the Journal of the American Medical Association — calling into question the effectiveness of merely yanking fruit flavors from shelves.

There’s been a “significant” increase in high schoolers’ reported use of mint- or menthol-flavored e-cigarettes from 2016 to 2019, “to levels near that of fruit-flavored e-cigarettes,” according to one of several new studies, which analyzed nationally representative data from more than 19,000 students who responded to this year’s National Youth Tobacco Survey.

Juul stopped selling fruity and sweet-flavored pods in brick and mortar stores in November 2018, but the pods were still available online to buyers 21 and over. Juul, which commands about three-quarters of the U.S. e-cigarette market, last month voluntarily stopped selling fruity and dessert-flavored vape pods (mango, creme, fruit and cucumber) online, admitting there was a “lack of trust” in the e-cigarette industry and signaling its intent to keep such products out of underage hands.

There’s been a ‘significant’ increase in high schoolers’ reported use of mint- or menthol-flavored e-cigarettes from 2016 to 2019, to levels near that of fruit-flavored e-cigarettes.

Some teens bought their favorite flavors on a black market for inflated prices and were spending $1,000 a year on their habit. Research suggests fruity flavors are a prime driver in getting young people to try vaping, a study by University of North Carolina at Chapel Hill School of Medicine found.

Mint also reigned as the most popular flavor among 10th- and 12th-grade Juul users and the second most popular flavor among eighth-grade users in 2019, according to a second study, which was funded by the FDA, the National Cancer Institute and the National Institute on Drug Abuse.

Nearly 28% of high schoolers and 11% of middle schoolers this year reported e-cigarette use within the past 30 days, the National Youth Tobacco Survey also found. More than half of those current e-cigarette users (59% of high-school users and 54% of middle-school users) said that Juul was their usual brand over the past month, according to the research, which was funded by the Food and Drug Administration and the Centers for Disease Control and Prevention.

The recently removed sweet and fruity flavors made up just under a 10th of the company’s sales, according to the Associated Press, and Juul is still selling its more-popular mint and menthol varieties.

“Our study calls into question whether regulations or sales suspensions of flavored e-cigarettes that exclude mint flavors would meaningfully reduce youth vaping,” lead study author Adam Leventhal, a professor of preventive medicine at the University of Southern California, said in a statement.

Juul did not respond to a MarketWatch request for comment on the two JAMA studies’ findings.

‘Our study calls into question whether regulations or sales suspensions of flavored e-cigarettes that exclude mint flavors would meaningfully reduce youth vaping.’

—Adam Leventhal, a professor of preventive medicine at the University of Southern California

The Trump administration reportedly plans to announce a ban on flavored vape products excluding menthol and tobacco flavors, according to Axios, which cited anonymous sources. The ban would reportedly include mint-flavored products. Juul “will support and comply with the final policy,” a company spokesman told the Wall Street Journal.

Among many claims in a wrongful-termination lawsuit filed last week by a former Juul executive was the allegation that company leadership had known that mint-flavored pods would compensate for a lack of sales from other flavors.

“You need to have an IQ of 5 to know that when customers don’t find mango they buy mint,” then-chief executive Kevin Burns allegedly told workers, according to the suit filed against Juul by Siddharth Breja, the company’s former senior vice president of finance.

Breja also claimed that the company had sold tainted batches of its mint-flavored products and refused to issue a recall or public-health notice to consumers.

Juul, which also did not respond to a request for comment on the lawsuit, previously told CNBC the company would “vigorously defend this lawsuit” and dismissed its allegations as “baseless.”

The new research comes as the CDC continues to investigate deaths and a lung-injury outbreak related to vaping. Some 1,888 cases have been reported from Washington, D.C. and every U.S. state except for Alaska as of Oct. 29, according to the agency, while 37 deaths across 24 states have been confirmed.

Most samples the FDA has tested contained THC, the psychoactive component in marijuana. Officials believe that THC-containing products, “particularly those obtained off the street or from other informal sources,” have played a significant part in the outbreak.