Martinez 2021.

Study characteristics
Methods	Design: RCT Recruitment: Participants were recruited throughout the USA through Facebook and multimedia advertisements (newspapers, radio, TV, e‐cigarette forums, and so on) for a study measuring attitudes and behaviours about cigarettes and e‐cigarettes Setting: USA Study start date: March 31 2015. Study end date June 30 2019
Participants	2896 dual users of nicotine EC and combustible tobacco cigarettes Assessment only n = 575;  generic smoking cessation booklets n = 1154; targeted booklets n = 1167. 37% female. Mean age 29.9  Mean cpd: 1 – 10 1663 (57%); 11 – 20 972 (34%); > 20 259 (9%). Mean ftnd 3.6. E‐cigarette use at baseline Inclusion criteria: age 18 years or older, smoked 1 or more combustible cigarettes per week over the preceding year, used e‐cigarettes 1 or more times per week over the preceding month, not currently enrolled in a face‐to‐face smoking cessation programme, and able to speak and read English. The original inclusion criteria required daily smoking. However, early in the trial, it became apparent that many dual users were skipping smoking on some days. Therefore, to better reflect the dual‐using population, we amended the use frequency criteria to equate them for smoking and vaping at 1 or more uses per week. The protocol was amended on 25 September 2016. We had recruited 652 participants up to that date. Participants were not necessarily seeking treatment or motivated to quit smoking or vaping. Participation was limited to 1 individual per street address. Participants gave oral informed consent
Interventions	EC type: n/a Assessment only (n = 575)   Generic smoking cessation self‐help booklets previously shown to be efficacious in smokers (n = 1154)  (an introductory Stop smoking for good brochure, 10 x Stop smoking for good didactic booklets, and 9 How I quit smoking pamphlets); Booklets specifically targeting dual users (n = 1167, (If you vape: a guide to quitting smoking), which included an introductory If you vape brochure, a series of 10 x If you vape: guide to quitting smoking booklets, and 9 x My story pamphlets). Participants assigned to the GENERIC or eTARGET groups were sent the intervention materials by post, with the option of also receiving them electronically
Outcomes	7‐day PPA at each assessment point. Sustained abstinence: 30‐day and 90‐day PPA Breath CO and saliva samples (for cotinine analysis) were collected at the 12‐ and 24‐month follow‐up points for participants who reported abstinence and resided within 100 miles of the home institution Cut‐offs of 8 ppm for CO and 10 ng/ml for cotinine were used to determine abstinence. The disconfirmation rates from this sample were used to estimate adjusted smoking rates for the full sample Full follow‐up assessments: 6, 12, 18, and 24 months.  Abbreviated assessments:3, 9, 15, and 21 months after baseline
Study funding	This work was supported by the National Institute on Drug Abuse of the NIH (R01DA037961). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH This work has also been supported in part by the Biostatistics and Bioinformatics Shared Resource and the Participant Research, Interventions, and Measures Resource at the H Lee Moffitt Cancer Center and Research Institute, a National Cancer Institute designated Comprehensive Cancer Center (P30CA76292)
Author declarations	Quote: "THB has received research support from the US National Institutes of Health (NIH), the American Cancer Society, the Florida Department of Health, and Pfizer; has collaborated on funded research with Voxiva, Optum, and the University of East Anglia (Norwich, UK); spent sabbatical at the Trimbos Institute and Utrecht University (Utrecht, Netherlands); is on the advisory board of, and holds restricted stock in, Hava Health, which is developing a pharmaceutical grade electronic nicotine delivery system for smoking cessation; participated in a Best Brains Exchange for Health Canada, providing advice on e‐cigarette policy; and consulted for the Australian Government Solicitor regarding plain tobacco packaging. UM has received research support from the NIH and the Galician Plan of Research, Innovation, and Growth (Spain); and has received funding from the Barrie Foundation to receive predoctoral training at the University of Newcastle (Callaghan, NSW, Australia). VNS has received research support from the NIH and the Florida Department of Health. SKS has received research support from the NIH, the American Cancer Society, the Florida Department of Health, and Pfizer. DJD has received research support from the NIH, the American Cancer Society, and the Florida Department of Health; and has provided paid expert testimony in litigation against tobacco companies. MMB has received funding from the NIH, the Florida Department of Health, the US Department of Veterans Affairs, the US Centers for Disease Control and Prevention, the National Science Foundation, and the US Department of Housing & Urban Development; and has received research support from Gilead Sciences, Florida Blue Foundation, Bristol Myers Squibb Foundation, Merck Foundation, Maine Cancer Foundation, and Pfizer. PTH has received research support from the NIH, US Food and Drug Administration (FDA), and Virginia Foundation for Healthy Youth. TE conducts research supported by the National Institute on Drug Abuse of the NIH and the Center for Tobacco Products of the FDA; is a paid consultant in litigation against the tobacco industry and the electronic cigarette industry; is named on one patent for a device that measures the puffing behaviour of electronic cigarette users and on another patent for a smartphone app that determines electronic cigarette device and liquid characteristics; owns shares in a variety of mutual funds, the exact stock makeup of which he has no control, and owns shares in three publicly traded companies, none of which are in any way related to the tobacco industry, the electronic cigarette industry, or any other aspect of this work; and has served as a special government employee of the US Government in the context of his service on the FDA’s Tobacco Products Scientific Advisory Committee and the Department of Health and Human Services Secretary’s Advisory Committee on Human Research Protection. CRB has received research support from the New Zealand Ministry of Health, the Health Research Council of New Zealand, CureKids Foundation, Heart Foundation, Health Promotion Agency, and Auckland Council and Sanitarium; collaborates on funded research with Newcastle University (Australia) through a grant from the Australian National Health and Medical Research Council, with Zhejiang University (Hangzhou, China) and Kunming University (Yunnan, China) on an Education New Zealand Tripartite grant, and with the University of Malaya (Kuala Lumpur, Malaysia) on a University of Malaya Grand Challenges grant; received funding from Pfizer Australasia for a survey of the impact of COVID‐19 on health workers in low‐income and middle‐income countries and from Johnson & Johnson Japan for consultancy on smoking cessation medication; and was a consultant to Moffit Cancer Center on this study through an NIH grant. LRM and KOB declare no competing interests. The employees of Moffitt Cancer Center—UM, VNS, SKS, DJD, LRM, KOB, MMB, and THB—are eligible for sharing of any revenue that might be generated by products developed during their employment, including the intervention used in this study."
Notes	New for Sept 2021 update Quote: "Participants were compensated US$10–20 for the first eight assessments and $40 for the final one, and they were eligible for $40–60 bonuses for completing at least seven assessments. Participants returning assessments within 1 week were sent inexpensive appreciation gifts.’ Appendix: ‘Participants were not aware in advance of the interview that they would be asked for biosamples, and new informed consent was obtained at that time. Participants received $20 for completing a biochemical verification interview and $15 for providing biosamples."
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "We used computer generated randomisation with balancedpermuted blocks (block size 10, with 2‐4‐4 ratio) to allocate participants to assessment only (ASSESS group), generic smoking cessation self‐help booklets (GENERIC group), or booklets targeting dual users (eTARGET group)."
Allocation concealment (selection bias)	Low risk	Computer‐generated (see above)
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Tailored versus generic booklet judged low risk as similar intensity; this is the comparison used in the meta‐analysis. Tailored versus no support would be high risk due to differential levels of support provided and no blinding
Blinding of outcome assessment (detection bias) All outcomes	Low risk	As above, tailored versus generic similar intensity so judged to be low risk of differential misreport (self‐reported cessation only)
Incomplete outcome data (attrition bias) All outcomes	Low risk	All > 50% at 24 months  ASSES: 361/575*100 = 62.8% GENERIC: 619/1154*100 = 53.6% eTARGET: 642/1167*100 = 55%
Selective reporting (reporting bias)	Low risk	All prespecified outcomes reported in the trial register reported in the publication