US candy manufacturer Juul Labs says the Juul device is now the preferred choice among youth for electronic cigarettes, replacing the traditional mint or menthol flavour.
The company said the choice was “markedly more favourable” than any other brand including menthol.
Juul said it had repeatedly met and communicated with regulators to share data on its products, including a new round of “sweepstakes” contests.
It said it would work with the Food and Drug Administration (FDA) to see if any changes are needed.
FDA vice-president Michael Taylor said his agency had some concerns about “the marketing and promotion” of the products.
Juul Labs introduced the starter kit – which costs about $300 in the US and includes the smokeless device – in August 2017, a month after Philip Morris International introduced its new iQOS electronic cigarette.
It has since become the most-subscribed e-cigarette app on the Apple App Store, generating free downloads of around 55,000.
The vaping trend has been linked to a rise in smoking in children and teenagers.
The number of middle-school and high-school students in the US who said they had used electronic cigarettes tripled between 2011 and 2017.
In May, the FDA said it was investigating Juul Labs’ marketing.
It has come under pressure from tobacco company Altria Group, which produces a rival product called MarkTen.
Juul Labs has been trying to prove to authorities that its product is safer than traditional tobacco cigarettes.
Earlier this year, it said it had received approval from the FDA to produce a pre-market review application that would allow it to be sold in the US without the need for a licence.
It introduced new designs to the product range, claiming there was less carbonation and no burnt tobacco, as well as taking suggestions from children and teenagers about what flavours they liked.
Juul Labs defended its “sweepstakes” contests, saying they had been an “important way” to raise awareness and provide educational opportunities.