Since the introduction of electronic cigarettes to the market in 2002, their global usage has risen rapidly. The global number of adult e-cigarette users rose from about 7 million in 2011 to 41 million 2018. Awareness and use of e-cigarettes greatly increased over the few years leading up to 2014, particularly among young people and women in some parts of the world. Since their introduction vaping has increased in the majority of high-income countries. E-cigarette use in the US and Europe is higher than in other countries, except for China which has the greatest number of e-cigarette users. Growth in the UK as of January 2018 had reportedly slowed since 2013. The growing frequency of e-cigarette use may be due to heavy promotion in youth-driven media channels, their low cost, and the belie