80 trials covering nearly 30,000 people found nicotine e-cigarettes gave smokers the best chance of quitting, raising success from about 6 in 100 to 1 in 10.
Nicotine vapes outperformed patches, gum, support plans and non-nicotine vapes, and may also beat the anti-smoking pill cytisine, though researchers said more evidence is needed on that comparison.
No increased risk of serious harm was found in the review, but researchers said the evidence applies to regulated products and warned unlicensed vapes can contain harmful chemicals or have unstable batteries.
5.4 million people in the UK now vape daily or occasionally versus 5.3 million smokers, even as doctors and the NHS say children and non-smokers should not vape and long-term risks remain unclear.
Smoking still kills more than 7 million people a year worldwide, making effective quitting tools a major public-health priority.