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. 2020 Jun 16;30(4):443–445. doi: 10.1136/tobaccocontrol-2019-055404

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© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

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Direct comparative risk (one question) compared with indirect comparative risk (two questions) of e-cigarette harms compared with cigarettes among all participants (current smokers, former smokers and never smokers).