When Food and Drug Commissioner Scott Gottlieb threatened to crack down on vaping products last month in response to "an epidemic of e-cigarette use among teenagers," he alluded to "preliminary data" showing that "youth use of e-cigs is rising very sharply." Although we still have not seen those numbers, that has not stopped Gottlieb from making policy decisions based on them, including changes that could limit the appeal and availability of products he concedes have enormous potential to reduce the harm caused by smoking.

"From 2017 to 2018, according to new preliminary data from the National Youth Tobacco Survey, the number of high-school-age children reporting use of e-cigarettes rose by more than 75 percent," Gottlieb and Secretary of Health and Human Services Alex Azar said in an October 12 Washington Post op-ed piece. They linked not to the NYTS results, which have not been released yet by the U.S. Centers for Disease Control and Prevention, but to a September 12 Post story that said, based on information from unnamed officials, "The latest data, not yet published, show a 75 percent increase in e-cigarette use among high school students this year, compared with 2017." In other words, Gottlieb backed up his claim about unpublished survey data by citing a leak to the Post that probably came from him or someone he authorized.

Gottlieb was less coy in an interview with CNBC on Friday. "We've seen a sharp spike in e-cigarette use among minors in the past year, from 2017 to 2018," he said. "Youth use…has increased 77 percent among high school students, around 50 percent among middle school students….When all the data comes in—we're going to be publishing it next month—it's going to look like around 20 percent of American kids are using e-cigarettes." Specifically, the Winston-Salem Journal reports, "about 20 percent of high school students" in the 2018 NYTS said they had used an e-cigarette "at least once over a 30-day period."

That's up from 11.7 percent in 2017, which would be a 71 percent increase. But it's not clear how many of those high school students were vaping often enough to get addicted to nicotine. In 2015, when past-month e-cigarette use peaked at 16 percent, 2.5 percent of high school students (16 percent of past-month vapers) reported vaping on 20 or more days in the previous month, and almost all of them were current or former smokers.

Gottlieb told CNBC the NYTS figures may underestimate the percentage of teenagers who vape because some of them may not recognize Juul, by far the most popular brand, as a kind of e-cigarette. "We think the figure might actually be underreported," he said, "because some kids, when you ask them if they use e-cigarettes, and they're using a Juul product, they refer to it as juuling…and they don't consider it an e-cigarette." I'm not sure how plausible that concern is, since the NYTS questionnaire, as of 2017, described e-cigarettes as "battery powered devices that usually contain a nicotine-based liquid that is vaporized and inhaled," adding that "you may know them as vape-pens, hookah-pens, e-hookahs, e-cigars, e-pipes, personal vaporizers or mods."

Critics have noted that the 2017 questionnaire did not include Juul on its list of brand examples, which were limited to NJOY, Blu, Vuse, MarkTen, Logic, Vapin Plus, eGo, and Halo. Did the 2018 questionnaire add Juul to the list? Gottlieb's comment suggests it did not, but we don't know for sure, because the CDC has not posted the questionnaire yet. Gottlieb said the 2019 questionnaire will include, at the FDA's request, a question about e-cigarette brands. But that does not answer the question of whether the 2018 questionnaire was revised in an attempt to identify Juul users who don't consider the product to be an "e-cigarette," "vape-pen," or "vaporizer." If the wording was revised, some of the increase that alarms Gottlieb could be due to that change.

Gottlieb expressed concern that some teenagers who vape will later move on to smoking. According to a CNBC story posted on Monday, which presumably also relies on information leaked by Gottlieb or his underlings, the 2018 NYTS found that "more high school kids are smoking cigarettes." Yet CNBC says the change in past-month smoking, from 7.6 percent to 8.1 percent, "is not statistically significant," meaning we can't confidently state that more high school kids are smoking cigarettes. CNBC reporter Angelica LaVito is untroubled by that detail. "Critics have warned a surge in e-cigarette use may cause nicotine-addicted kids to migrate to conventional cigarettes," she writes. "The new data suggest this may be happening."

Smoking by teenagers has in fact been declining for years, notwithstanding a sharp rise in e-cigarette experimentation, and last year reached a record low. In this context, it is reasonable to question the public health significance of the statistically insignificant blip that Gottlieb or someone else at the FDA described to CNBC. But that sort of analysis is hard to do as long as we are limited to secondhand accounts of the survey results.

If Gottlieb does release all of the relevant NYTS data, along with the questionnaire, next month, we should have answers to these questions. In the meantime, he is making policy decisions that could affect adult smokers' access to vaping products based on data the public is not allowed to examine.

It is hard to be sanguine about Gottlieb's use of this secret information after watching the CNBC interview. He talked about banning online sales of e-cigarettes, for example, even though online vendors such as Juul use age verification systems and the vast majority of illegal sales to minors occur in brick-and-mortar stores (as Gottlieb conceded).

"We recognize [e-cigarettes] as a viable alternative for adults smokers who want to get access to satisfying levels of nicotine without all the harmful effects of combustion," Gottlieb said. "If we could switch every adult smoker to an e-cigarette, it would have a profound public health impact." Yet he is ready to discourage that switch by making e-cigarettes less appealing (by restricting flavors, for example) and harder to get (by banning sales outside of adults-only vape shops, another idea he floated), all based on an "epidemic" that is impossible to evaluate without the data he is not letting us see.