Fig. 1

a Transitions between smoking states in the No-NVP Scenario. b Transitions between regular smoking and nicotine vaping product use states in the NVP Scenario. NVP, nicotine vaping product. ^aSmoking initiation includes initiation into regular cigarette use net of any experimental NVP use and includes those who become regular dual users who smoke and regularly use NVPs. ^bNVP initiation includes initiation into regular NVP use net of any experimental cigarette use. ^cSwitching after age 35 includes those regular smokers who quit smoking and switch to regular NVP and are considered before former smokers using NVPs. ^dSwitching before age 35 includes those regular smokers who quit smoking and switch to regular NVP use, and considered exclusive NVP users due to the reduced risks of quitting smoking before age 35. ^eSmoking cessation includes cessation from regular cigarette use and dual users who quit both cigarette and NVP use, but may include those who quit smoking and temporarily use NVP. ^fFormer smoker using NVPs cessation includes those former smokers who quit NVPs and remain former smokers. NVP cessation includes those exclusive NVP users who quit NVP use