Before COVID-19 was dominating headlines, many Americans were concerned about another deadly epidemic: vaping.
It's been linked to more than 2,800 hospitalizations and deaths, though health officials haven't linked any specific substance or products to the illnesses, and no single product has been associated with all of the cases.
E-cigarette sales in the United States steadily rose from 2016 to 2018, with youth-friendly, candy- and fruit-flavored products that critics say targeted teens fueling most of that growth. Facing mounting criticism as reports of vaping-associated lung disease rose, the popular vaping brand JUUL ended in-store sales of fruit- and candy-flavored products in November 2018.
But, according to a new study, those actions have had little effect. Sales of e-cigarettes remain strong even after the measures taken to curb purchases of youth-friendly products, raising questions about federal regulations and how to best protect American youth from harming themselves by vaping.
After companies stepped in to self-regulate, e-cigarette sales dropped for about two months but quickly rebounded, soon exceeding previous highs, according to the study by the American Cancer Society published in the American Journal of Public Health.
The study's authors said the data show a glaring shortcoming in allowing e-cigarette companies largely to self-regulate in lieu of coordinated federal regulations. In December, more than a year after JUUL stopped selling fruit- and candy-flavored products, Congress did ban the sale of all tobacco and e-cigarettes to anyone younger than 21.
A spokesperson for JUUL told ABC News that the company is working closely with regulators, attorneys, public health officials and other stakeholders to combat underage use of its products and "will continue to reset the vapor category in the U.S. and seek to earn the trust of society." Juul has also long maintained its products are intended for adults looking to switch from combustible cigarettes.
The Food and Drug Administration, which regulates tobacco products, said it was reviewing the findings of the recent study, which will be evaluated as part of a larger body of evidence.
The study, based on sales figures from the market research firm Nielsen, only collected data from brick-and-mortar retailers and may not show the whole picture. Online sales of vaping products could be much higher, especially among younger buyers, according to experts.
"The trends being reported in this paper are likely to be an underestimate of the total volume of sales across the country," said Dr. Andy Tan, a public health researcher at Dana-Farber Cancer Institute.
The study didn't track purchases by individual customers and wasn't broken down into age groups. Nevertheless, the data offers a "snapshot" of e-cigarette sales over time in certain stores and suggests vaping continues to be popular despite the voluntary removal of fruit- and candy-flavored products by e-cigarette companies, Tan noted.
Outside surveys have corroborated the idea that many middle school and high school students simply switched to mint, menthol and tobacco flavors. Believing that the removal of a few flavors of a highly successful product would make a significant dent in usage is "highly naive," Tan added, "because these products are highly addictive."
Alex Liber, one of the study's lead scientists, added: "JUUL was able to transition sales of other flavors easily by simply swapping which flavors were being displayed in stores."
JUUL's sales also likely got a boost, Liber added, thanks to new part-owner Altria, a massive distributor of tobacco products that also owns Philip Morris USA, the producer of Marlboro cigarettes.
From 2016 to 2019, according to a National Youth Tobacco survey, flavor preferences among high school students shifted, with those vaping menthol or mint flavors increasing to 57% from 16%.
Ultimately, the researchers concluded that JUUL's self-regulation was insufficient to curb the use of these products, although it's too soon to determine how big of an impact changing the legal purchasing age to 21 may have.
"Business acts to serve its own interests," Liber said, "while well-constructed government regulation can serve the public interest."
Heather J. Kagan, M.D., an internal medicine resident physician at The Johns Hopkins Hospital, is a contributor to the ABC News Medical Unit. Sony Salzman is the unit's coordinating producer.