Background Globally, tobacco smoking remains the largest cause of premature death. The COVID-19 pandemic has forced nations to take unprecedented measures including 'lockdowns' that might impact tobacco smoking behaviour. We performed a systematic review and meta-analyses to assess smoking behaviour changes during the early phases of the COVID-19 pandemic. Methods We searched Medline/Embase/PsycINFO/BioRxiv/MedRxiv/SSRN databases (January-November 2020) for published and pre-print articles that

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... reported specific smoking behaviour changes or intentions after the onset of the COVID-19 pandemic. We used random-effects models to pool prevalence ratios comparing the prevalence of smokers during and before the pandemic, and the prevalence of smoking behaviour changes. Results 33 studies were included in meta-analyses, with smoking data for ∼230,000 participants across 24 countries. The proportions of smokers during and before the pandemic were similar, with a pooled prevalence ratio 0.85 (95%CI:0.76-0.95). In studies limited to smokers, 27% (95%CI:21-32%) smoked more, 17% (95%CI:13-21%) smoked less, 54% (95%CI:47-61%) smoked the same and 5% (95%CI:2-9%) reported quitting smoking. Among all participants, 1% (95%CI:0-2%) started smoking during the pandemic. All studies were at high risk of bias due to use of non-representative samples, likely non-response bias, and utilisation of non-validated questions. Conclusions Smoking behaviour changes during the early phases of the COVID-19 pandemic were highly mixed. Meta-analyses indicated slightly lower overall smoking prevalence during the pandemic, but higher intensity among smokers. Key messages More recent and higher quality studies of smoking behaviour changes are required to measure the longer term impact of the COVID-19 pandemic.