Modelling a tobacco-free generation policy in Australia: population health impacts under illicit market uncertainty

Objective To estimate the potential health and equity impacts of a tobacco free generation (TFG) and T21 policy (increasing the legal age of sale to 21) in Australia, in the context of a complex market including widespread illicit tobacco and e-cigarette product availability. Design A Markov macrosimulation model, parameterised with yearly net movements between legal smoking, illicit smoking, vaping, and dual use states, combined with a proportional multi-state lifetable. Setting The Australian population, modelled as an open cohort for 40-years. Intervention A 'business-as-usual' (BAU) scenario was compared to TFG and T21 policies, with both starting in 2026. Variations to policy impacts were tested under increasing background illicit market enforcement. Main outcome measures The model estimates the health-adjusted life years (HALYs) and deaths over 40 years, under each scenario, with differences across age and socioeconomic status (SES) presented. Results The TFG policy reduced daily smoking prevalence among 15-24-year-olds to 4.6% (95% uncertainty interval [UI] 3.8-5.7%) in 20 years' time, compared to 7.2% under the T21 policy and 7.9% under BAU trends. Vaping was minimally impacted by either policy. The TFG policy resulted in 178,000 (95% UI 87,800-314,000) HALYs being gained over 40 years. The policy impact was largest when accompanied by increased illicit market enforcement, reducing daily smoking among 15-24-year-olds to 1.4% within 20 years. Both policies had greater prevalence and health impacts on more disadvantaged compared to advantaged SES groups. Conclusion A TFG policy is expected to produce long-term benefits for the Australian population but would be most effective in combination with increased enforcement of illicit tobacco and e-cigarette markets. Novel strategies to increase quitting in addition to reducing uptake are needed to improve tobacco-related outcomes in the short to medium term.