As yet, there is little evidence that e-cigarettes are a gateway to tobacco or other drugs, or that use is common among children, the summit heard. According to the STS, e-cigarette use by age follows a similar pattern to smoking. “We are not seeing a huge bulge in young people using e-cigarettes,” Professor West commented.

STS found that 2.9 and 3.6 per cent of long-term ex-smokers had used e-cigarettes and nicotine replacement therapies (NRT) respectively. Just 0.2 per cent of never-smokers had used e-cigarettes. The same proportion of never-smokers had tried NRT. “E-cigarette use by never smokers is negligible and similar to NRT use,” Professor West said.

Linda Bauld, professor of health policy at Sterling University, commented that ‘ever use’ rates of e-cigarettes among children varied from 5 to 62 per cent in surveys undertaken in various countries between 2011 and 2014 (the figure of 62 per cent comes from Poland). Professor Bauld noted that, with the exception of the Polish study, rates of regular use are commonly less than 10 per cent – and most of these also smoke. “Current use in never smokers also remains low,” she added. The highest rate is 2 per cent.

Nevertheless some teenagers do experiment with e-cigarettes rather than tobacco. “Until we have reliable longitudinal data on young people and e-cigarettes, theories about these products being a ‘gateway’ to smoking are just that – theories,” Professor Bauld said. “However we need to recognise that a number of young people are exposed to nicotine for the first time by using an e-cigarette.”