Conflict of Interest: C. Notley has nothing to disclose. Conflict of interest: A.R. Butler reports payments made to institution to fund her role on the living systematic review of e-cigarettes for smoking cessation from Cancer Research UK (CRUK). Conflict of interest: N. Lindson reports that her salary is paid by the University of Oxford through a grant from the UK National Institute for Health Research (NIHR); she is co-PI on a grant to carry out a Living Systematic Cochrane Review of ‘Electronic Cigarettes for Smoking Cessation’ funded by CRUK (current); PI on a programme grant to carry out a systematic review and network meta-analysis to investigate the safety and efficacy of pharmalogical treatments and electronic cigarettes for smoking cessation funded by the NIHR (current); co-applicant on a grant to investigate youth uptake of electronic cigarettes funded by CRUK (current); co-applicant on an infrastructure grant which funds the Cochrane Tobacco Addiction Group funded by NIHR (current); co-applicant on a grant to investigate the comparative effectiveness of behavioural smoking cessation treatments funded by NIHR (ended Jan 2021); and receives payment for teaching Cochrane authors how to write Cochrane protocols on behalf of Cochrane UK (not for profit organisation) (current) funded by Oxford Universities NHS Foundation Trust. Conflict of interest: C. Bullen reports research grants paid to institution (University of Auckland) from Health Research Council of NZ; contract for smoking cessation guideline review, paid to institution from NZ Ministry of Health; contract for smokefree plan, paid to institution from Auckland Council; contract for research, paid to institution from Pfizer; research grant paid to institution from Tencent; personal fees for consulting on new NRT product from Johnson & Johnson KK (Japan); lecture fees for Lecture at Ottawa Heart Institute Annual conference, and honoraria for manuscript writing Simon Fraser University; is president of SRNT-Oceania (unpaid); and tobacco expert advisory group member, Health Coalition Aotearoa (unpaid). Conflict of interest: A. Theodoulou has nothing to disclose. Conflict of interest: R. Begh has nothing to disclose. Conflict of interest: H. McRobbie reports grant payments made to institution from Health Research Council (NZ), NIHR (UK) and NHMRC (AUS), outside the submitted work; and received honoraria from Pfizer for speaking at smoking cessation educational events and an advisory board meeting in October 2018. Conflict of interest: P. Hajek reports honoraria from Pfizer for contributing to Pfizer Workshop at SRNT Conference. Conflict of interest: N. Rigotti reports contract for clinical trial paid to institution from Achieve Life Sciences; personal royalties for review of e-cigarettes from UpToDate; personal consulting fee from Achieve Life Sciences. Conflict of interest: J. Hartmann-Boyce reports grant funding, including to support the review which this letter refers to paid to institution from Cancer Research UK; grant funding unrelated to this work paid to institution from British Heart Foundation; grant funding, including to support the review which this letter refers to, paid to institution from NIHR.