Background: Policy decisions should be evidence-based, but the magnitude of intended and unintended impacts cannot always be easily estimated from the available data. For example, banning flavours in electronic cigarettes (e-cigarettes) to reduce appeal to non-smoking young people could have the intended impact by reducing youth vaping but could have negative consequences for adult smokers and vapers. Methods: We developed a decision aid to help policymakers make informed decisions on the potential net impact of a ban on e-cigarette flavours. We estimated the number of non-smoking youth who would be deterred from ever vaping and subsequently ever smoking, and the number of smokers and ex-smokers who would be deterred from quitting or encouraged to relapse, to determine whether the benefits to youth outweigh the costs to existing smokers and vapers. This aid then outputs a report with the results graphically depicted to aid interpretability. Results: We demonstrated the value of this decision aid using data from various sources to estimate the impact of a flavour ban in three populations: the general UK population, low-socioeconomic position UK population, and the general US population. All three examples suggested a negative net population impact of a ban. These reports were then presented to the all-party parliamentary group for vaping. Discussion: We demonstrate how decision aids can be used to help policymakers arrive at evidence-based decisions efficiently and can be used to quickly obtain up-to-date estimates as new data becomes available.

The authors have declared no competing interest.

This work was originally supported by Public Health England (PHE) via an honorary contract awarded to ASA. There is no grant number for this research as it was commissioned by Public Health England via the honorary academic framework. Further support was received from the University of Bristol via an Economic and Social Research Council Impact Acceleration Award (A100111) awarded to JNK, ASA and MRM. MJG and MRM are supported by the Medical Research Council Integrative Epidemiology Unit (MC_UU_00011/7). JNK is supported by a Cancer Research UK programme grant (the Integrative Cancer Epidemiology Programme C18281/A29019).

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