A nationwide ban on many flavored e-cigarette products goes into effect Thursday, but teenagers will still have access to nicotine vapes, experts say.

The ban covers a number of kid-friendly flavorings, such as mint and fruit, though menthol and tobacco flavorings will remain legal. However, the ban only applies to specific types of devices: cartridge or pre-filled pod devices, like the ones made popular by Juul. All other devices will be left on the market.

But limiting access to Juul, which stopped selling all non-menthol and tobacco flavored pods in November, is unlikely to have much of an effect on teens already addicted to nicotine.

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"Kids have moved on," Meredith Berkman, co-founder of Parents Against Vaping E-cigarettes, or PAVE, told NBC News.

Teenagers know that teachers are now educated about how to detect vaping in classrooms, she said. So they're getting their nicotine fix in other ways, including products not covered by the looming ban.

"Kids are sucking on flavored nicotine pouches to get through the day until they can get home to their device," Berkman said. The pouches are reminiscent of chewing tobacco, but are advertised as being "tobacco-free."

Experts in teen addiction also said there's plenty of evidence that teens now favor highly concentrated, refillable nicotine vape products called Smok and Suorin Drops as well as cheaper, disposable vape pods called Puff Bars — also to be left on the market after Thursday.

"I'm not very optimistic," Bonnie Halpern-Felsher, a professor at Stanford University who studies teen vaping, said. "We really do need to have enforcement of the law across all tobacco products, regardless of these loopholes."