The past decade in British healthcare has been disappointing: improvements in life expectancy and neonatal mortality have stalled and public satisfaction with the NHS has fallen sharply.

But one positive singled out in a recent review of healthcare developments was the rise of e-cigarettes use, which the article noted had given “tobacco cessation a boost at no cost to the public purse”.

Yet 2019 was one of the most challenging years for e-cigarettes since they emerged on the global market just over 10 years ago. The controversy about their risks and benefits shows no sign of abating and more countries have taken action to ban them. So what happened in 2019 – and what’s next?

The most worrying development came from the US, where a spectrum of serious respiratory diseases – and even deaths – linked to the devices emerged, becoming known as Evali (e-cigarette or vaping associated lung injury). The outbreak began in June 2019 and peaked in September. As of mid-December, 54 deaths and 2,506 hospital cases had been reported. Most of the cases were in young adults and in the early months the advice issued by the Centres for Disease Control and Prevention was that vapers should stop using the products immediately.

This outbreak triggered substantial alarm about the health risks of vaping, not just in the US but around the world. Were we only now seeing the real consequences of these products that had been used for about a decade by up to 10 million Americans?

Yet as the investigation proceeded, it became clear that it was not nicotine vaping that was implicated. Details were slow to emerge because the substances involved were in fact cartridges containing cannabis (primarily tetrahydrocannabinol or THC). These were often obtained on the illicit market, and in some cases being used by children. This meant users were reluctant to admit what they had vaped.

Finally, in December, the CDC conceded that there was sufficient evidence to conclude that most cases of Evali had been caused by a specific additive in cannabis vaping products, vitamin E acetate, which can be harmful when inhaled. Some researchers and cannabis industry experts had been pointing to this cause since the summer, but their advice had largely been ignored. No similar cases were identified anywhere outside North America. In the UK and Europe, for example, THC vaping and vitamin additives are illegal and the market is much more tightly regulated.

The Evali outbreak coincided with reports of increases in rates of vaping among teenagers in the US, a trend that had begun some years before, but has quickly accelerated. Critics pointed to the popularity of the myriad e-cigarette flavours and the rise of discreet vaping products, particularly Juul.

The response from policymakers was swift, with first San Francisco and then several US states imposing de facto bans on sales, and major retailers removing the products from their shelves. While these developments were confined largely to the US, the resulting global media coverage undoubtedly contributed to the decision of other countries to crack down on vaping.

India announced a ban, followed by the Philippines – two countries with millions of tobacco users. Canada, where e-cigarettes had recently been legalised, began to retreat from a harm reduction approach and several provinces announced sweeping restrictions.

The focus now in most parts of the world is on protecting young people, particularly non-smokers, from e-cigarette uptake – although surveys suggest regular vaping in this group is still rare. The world’s 1.4 billion smokers often become a secondary consideration, despite evidence that former and current smokers make up the vast majority of e-cigarette users. Market analysts who until recently were predicting continued growth in the global e-cigarette market are now much less bullish.

But as 2019 draws to a close there is some good news. For the first time, the World Health Organisation reported that tobacco use among men has stopped growing globally. Rates of use among women began declining some time ago. Tobacco control measures are working.

In the UK, vaping has been credited with contributing to recent reductions in smoking. Studies published in 2019 showed that e-cigarettes help smokers quit and can benefit cardiovascular health. Even in the US, recent research suggests any rise in youth vaping has coincided with sharp declines in young people smoking.

The ideal combination is proportionate regulation of e-cigarettes combined with effective implementation of tobacco control. As a new decade dawns, more countries need to achieve this balance. If they do not, the opportunity presented by e-cigarettes will be lost. And many smokers who have struggled to stop and who might otherwise have quit with vaping will be resigned to the death and disease that tobacco causes.

• Prof Linda Bauld is the Bruce and John Usher chair of public health in the Usher Institute, University of Edinburgh, and holds the CRUK Bupa chair in behavioural research for cancer prevention at Cancer Research UK.

• Dr Suzi Gage is a senior lecturer at the University of Liverpool, researching links between substance use and mental health. Her first book Say Why to Drugs is published in January 2020.