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Pooled results for nicotine abstinence, allocated product use and smoking cessation. Studies: Bonevski et al. (2021) [14], Bullen et al. (2013) [17], Hajek et al. (2019) [18], Lee et al. (2018) [20]. EC: e-cigarette; df: degree of freedom; M–H: Mantel–Haenszel; NRT: nicotine replacement therapy.
