The number of vapers in Great Britain has topped three million for the first time - four times the number in 2012, according to a survey by Action on Smoking and Health. Most use e-cigarettes because they have quit smoking and 40% are smokers who are trying to give up. The estimations are based on a survey of 12,000 British adults. But a "worrying" belief that vaping is as bad as smoking still exists, a King's College London analysis found.