The US state of Massachusetts upheld a ban on e-cigarettes on Friday amid a spate of deaths and injuries linked to vaping across the country.
Eighteen deaths in 15 states had now been positively linked to vaping since March, from a total of 1,080 illnesses, according to the Centres for Disease Control and Prevention.
Officials in Connecticut also announced a further death in that state on Friday.
Massachusetts became the first American state to issue an outright ban on all e-cigarette devices in September, with the prohibition to last for four months.
Manufacturers sought to challenge the ban in a Boston court, arguing that the law was disproportionate to the health risks posed by the devices.
The Vapor Technology Association instead called for a limited prohibition on certain products, including black market refills and devices for vaping tetrahydrocannabinol (THC), the primary psychoactive substance of marijuana.
But the court rejected the application for an interim lifting of the ban, saying it would “conflict with the public interest”. A full hearing of the case will be held on October 15.
E-cigarettes have been available in the US since 2006.
Initially conceived as a smoking cessation device, e-cigarette use has skyrocketed among teens, with preliminary official data for 2019 showing more than a quarter of high school students using e-cigarettes in the past 30 days.
They were until recently perceived as a less harmful alternative to smoking because they do not contain the 7,000 chemicals in cigarettes, dozens of which are known to cause cancer.
It is not clear whether the outbreak of vaping-related illnesses is only happening now, or if there were cases earlier that were wrongly diagnosed.
Only one case of lung injury has been reported abroad, making the outbreak more mysterious still.
Public and political opinion appears to be hardening, however, with the administration of US President Donald Trump announcing in September that it would ban flavoured e-cigarette products in the coming months.