Table 1 Trials of call‐back counselling interventions.

Study/country		Population (follow‐up rate)		Intervention(s)		Control		Criteria for cessation
Borland et al, 20017 Australia		998 callers to Victorian quitline (66%)		Additional calls, 2 or more according to need, average 2.8		Motivational counselling at initial call, self help materials		Quit at 12 months (sustained for 9 months)
Borland et al, 20038 Australia		1051* callers to Victorian quitline (76%)		Additional calls usually over 2–3 weeks, average 4.8		Quit pack and 3 mailings of tailored letters, possibility of brief counselling at initial call		Quit at 12 months (sustained for 9 months)
Gilbert et al, 20069 United Kingdom		1457 UK quitline callers (63%)		Up to 5 calls over 4 weeks. 26% received none, 42% received ⩾4		Counselling at initial call, self help materials		Quit at 12 months (sustained for 6 months)
Hollis et al, 200510 United States		4614 Oregon quitline users (69%)		Factorial trial of free NRT and 3 levels of counselling(1) Moderate counselling; 30–40 minutes motivational interview, brief 2nd call, tailored self help.(2) As (1) plus offer of 4 further calls		Brief 15‐minute telephone counselling, self help materials and referral information, +/− NRT		Quit at 12 months (for >30 days)
Rabius et al, 200411 United States		3522 quitline callers (∼66% at 3 months)		5 calls over 2 weeks (Stanford model)		Self help materials		Quit at 6 months (for 3 months)
Smith et al, 200413 Canada		632 quitline callers (73% print only, 62% counselling at 12 months)		(1) 50‐minute initial call then 2 5–10‐minute calls at 2 and 7 days		Self help materials		Quit at 12 months (sustained)
				(2) As (1) plus 4 further calls at 14, 21, 35 and 49 days (factorial with self help variants)
Zhu et al, 199614 United States		3030 California quitline callers (86%)		(1) single 50‐minute call pre‐quit date		Self help materials		Quit at 13 months (for 12 months)
				(2) As (1) plus up to 5 further calls over 1 month
Zhu et al, 200215 United States		3282 California quitline callers seeking counselling (71%)		Up to 7 calls over 3 months, First session pre‐quit (72% received at least 1 call average 3 sessions		Self help materials. Telephone counselling also provided if requested (32% received)		Quit at 13 months (for 12 months)
Rabius et al, 2006†12,21		6322 American Cancer Society quitline callers (52%)		3×2 factorial trial of session length and use of boosters		Self help materials only		Quit at 6 months
Zhu et al 2004†16		1101 pregnant women calling California smokers' helpline		Up to 7 counselling calls (1 pre‐quit, up to 6 follow‐up).		Quit kit including American Cancer Society booklet for pregnant smokers		Quit for ⩾30 days at 3rd trimester evaluation

NRT, nicotine replacement therapy.

*In relevant arms.

†Not included in meta‐analysis.