Hartmann-Boyce J, McRobbie H, Lindson N, Bullen C, Begh R, Theodoulou A, Notley C, Rigotti NA, Turner T, Butler AR, Hajek P. Electronic cigarettes for smoking cessation. Cochrane Database Syst Rev. 2020 Oct 14;10:CD010216. doi: 10.1002/14651858.CD010216.pub4. PMID: 33052602.

This Cochrane systematic review of 50 studies found that electronic cigarettes with nicotine are more effective at helping people quit smoking than those without nicotine.

https://pubmed.ncbi.nlm.nih.gov/33052602/