Every year, the number has gone up — from 11% in 2017 to 21% in 2018 to 25% this year. That is the share of high school seniors who admit to having used e-cigarettes in the past month. And it’s not just almost-18-year-olds who are vaping: A fifth of 10th-graders report doing so in the past month.

E-cigarettes vaporize a nicotine-rich — or, increasingly, a THC-laced — liquid, and when they first came on the market, all many people saw was the upside. Finally there was a product that allowed smokers to mimic the act of smoking a traditional, combustible cigarette but with apparently fewer toxic chemicals.

When the Food and Drug Administration moved to regulate the industry, critics warned that the federal government was poised to crush mom-and-pop e-cigarette purveyors selling innovative products that improved their customers’ health.

Now, the downside is becoming alarmingly clear, and state and federal governments are beginning to crack down — later, perhaps, than they should have. Teenagers have begun to vape at astonishing rates, confident that their e-cigarettes are “safe” compared with combustible ones. Nicotine affects adolescent brains uniquely, and e-cigarettes can hook children on nicotine for life, an addiction that could lead to consuming other tobacco products whose risk profile is well-established and highly dangerous.

It is for this rising generation that regulation is most necessary — and concern for them should trump worries about reducing smokers’ access to the smoking alternatives they prefer.

That is why the news that Massachusetts Gov. Charlie Baker, a Republican, issued a temporary ban on the sale of all vaping products in his state is welcome. Baker’s decision comes on top of the FDA’s move to ban e-liquid flavors other than tobacco nationwide, which draws on experience showing that young vapers prefer flavored products. The governor and Massachusetts public health authorities must take care that teenage vapers hooked on nicotine do not seek traditional cigarettes as a substitute.

Their move to require health coverage for tobacco cessation products such as nicotine gums and patches is a good start, but that measure is not targeted at addicted youth. Less important are concerns that vape store entrepreneurs now must shut down or weather several dry months; the priority must be to prevent evermore teenage addicts.