In 2013 the group published the tobacco policy review Tobacco Free Ireland, a report that set Ireland’s goal to reduce smoking prevalence to less than 5% by 2025. The report identified tobacco damage reduction as an important issue to consider. Since the introduction of e-cigarettes in the European Union (EU) in 2006 and the United States of America (USA) in 2007, research has been conducted into their potential benefits in terms of reducing tobacco and public health harm of e-cigarettes -cigarettes has grown. The systematic evidence analysis reported in this article outlines what is known so far about the consumption of e-cigarettes and the onset of smoking from tobacco cigarettes in adolescents. There are two sister reviews: the first shows the harms and benefits of e-cigarettes [McCarthy 2020] and the second presents a systematic overview of the role of e-cigarettes in smoking cessation [Quigley 2020] . These reviews are one of the contributions to the Irish Government’s policy and clinical guidance on e-cigarettes.
Our systematic review published in BMC Public Healthfound that e-cigarette use among teenagers in Europe and North America is linked to the onset of tobacco smoking. Based on the adjusted odds ratios of nine primary studies, our meta-analysis calculated that teenagers who had ever used e-cigarettes at the start of the study were three to six times more likely to start smoking. These results identify an important health-related harm and are supported by four additional systematic reviews. [Soneji 2017; Glasser 2019; Khouja 2019; Aladeokin and Haighton 2019] Three of these ratings were from young adults [Soneji 2017; Glasser 2019; Khouja 2019] and one was with teenagers living in the UK [Aladeokin and Haighton 2019] . These results are important as the prevalence of e-cigarette use increases in Europe and North America. For example, the prevalence of e-cigarette use among teenagers in the United States rose from 1.5% in 2011 to 20.8% in 2018 [Cullen 2018] and in Ireland usage is 22% [Költő 2020] . In addition, there is a danger that society will not be able to protect the advances in tobacco smoking reduction among teenagers.
The study provides additional support for urgent responses from policy makers to cease teenage use in order to reduce direct harm in this vulnerable population group.
Given the availability and use of e-cigarettes, this study provides additional support for urgent policymaker responses to cease their use by teenagers in order to reduce direct harm in this vulnerable population. The study presented in this paper was conducted as part of a wider evidence review program to inform and support public health policy in Ireland that included mapping the harms and benefits of e-cigarettes (and their e-liquids) [McCarthy 2020] and a systematic review of the role of e-cigarettes in smoking cessation [Quigley 2020] . We found that e-cigarettes (and their e-liquids) lead to acute harm such as poisoning, lung injuries, burns, and blast injuries, a finding that is consistent with six other aligned systematic reviews [Peruga 2020; National Academies of Sciences, Engineering, Medicine2018, Pisinger 2014; CADTH 2017; Byrne 2018; Bals 2019] and stressed the need for further studies with robust methods to measure the long-term health effects of their use, as these are not yet known.
Children and adolescents need the same protection from e-cigarettes as conventional tobacco cigarettes
Children and adolescents need the same protection from e-cigarettes as traditional tobacco cigarettes through a well-enforced regulatory system of measures, including age restrictions on purchases, control of availability through licensors, restrictions on product visibility and attractiveness, and reasonable pricing through taxation.
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