The UCL team has been tracking the rapid rise in use of e-cigarettes using monthly national surveys and estimates that in 2014 almost 900,000 smokers used one of these products to try to quit (see "Electronic cigarettes in England - latest trends" (ref STS140122) at http://www.
Previous research has found that when used in this way, e-cigarettes increase the chances of success by around 50% compared with using no support or one of the traditional nicotine products such as gum or skin patch bought from a shop.2,3 This raises the long-term success rates from around 5% to around 7½%. The increased success rate amounts to an additional 22K people stopping who would otherwise have continued smoking. Some of these people may have used an e-cigarette instead of one of the more established aids to cessation such as the Stop-Smoking Services. Adjusting for this, the number helped by e-cigarettes may be somewhat lower, at 16K.
Professor Robert West, who led the research team, said "E-cigarettes appear to be helping a significant number of smokers to stop who would not have done otherwise - not as many as some e-cigarette enthusiasts claim, but a substantial number nonetheless."
Professor West added, "There have been claims by some public health researchers that e-cigarettes undermine quitting if smokers use them just to cut down, and that they act as a gateway into smoking. These claims stem from a misunderstanding of what the evidence can tell us at this stage, but this is clearly something we need to watch carefully."
1West R, Shahab L, and Brown J (2016). Estimating the population impact of e-cigarettes on smoking cessation in England. Addiction 111: DOI: 10.1111/add.13343.
2McRobbie H, Bullen C, Hartmann-Boyce J, and Hajek P (2014). Electronic cigarettes for smoking cessation and reduction. Cochrane Database of Systematic Reviews, Issue 12. Art. No.: CD010216. DOI: 10.1002/14651858.CD010216.pub2.
3Brown J, Beard E, Kotz D, Michie S, and West R (2014). Real-world effectiveness of e-cigarettes when used to aid smoking cessation: A cross-sectional population study. Addiction 109(9), 1531-40. DOI: 10.1111/add.12623.