Table 3 Quality of Evidence of Outcomes of Restrictions on the Sale of Flavoured ENDS

Reduced sales of ENDS

Moderate

Dose-response gradient (ban on all ENDS vs. flavours) (+ 1)

Large magnitude of effect (+ 2)

Limitations in study design (− 1)

Potential publication bias (− 1)

Ali (2022), Gammon (2021), Katchmar (2021), Liber (2021) [28,29,30,31]

Increased sales of combustible cigarettes

Low

Dose-response gradient (ban on all ENDS vs. flavours) (+ 1)

Moderate magnitude of effect (+ 1)

Inconsistent findings (− 1)

Limitations in study design (− 1)

Gammon (2021), Katchmar (2021), Liber (2021), Xu (2022) [28,29,30, 33]

Reduced consumption of any tobacco use

Low

Moderate effect sizes across studies (+ 1)

Inconsistencies in measurement rigour (differing definitions of product use) (− 1)

Low measurement rigour (− 1)

Kingsley (2019, 2021), Olsen (2022), Yang (2022) [38,39,40,41]

Reduced ENDS consumption

Low

Moderate effect sizes across studies (+ 1)

Inconsistencies in measurement rigour (differing definitions of product use) (− 1)

Low measurement rigour (− 1)

Hawkins (2021), Kingsley (2019), Liu (2022), Yang (2020) [35, 38, 39, 42]

Increased combustible cigarette consumption

Very Low

Large magnitude of effect (+ 2)

Limitations in study design (− 1)

Inconsistency in controls for bias risk (− 1)

Inconsistent findings (− 1)

Low measurement rigour (differing definitions of product use) (− 1)

Friedman (2021), Hawkins (2021), Kingsley (2019), Liu (2022), Yang (2022) [34, 35, 38, 39, 42]

Reduced availability of flavoured products

Moderate

Dose-response gradient (difference in enforcement) (+ 1)

Large magnitude of effect across studies (+ 2)

Limitations in study design (−1)

Inconsistencies in measurement rigor (short-term follow-up) (− 1)

Amalia (2020, 2020), Andersen-Rodgers (2021), Brock (2019), Gaiha (2021), Holmes (2022), Kephart (2020), Kingsley (2019), Nali (2021), Vyas (2021) [39, 53,54,55,56,57,58,59,60,61]