E-cigarettes have long been pitched as a healthier alternative to cigarettes, and one that could help smokers kick the habit by delivering nicotine without many of the dangerous byproducts of combustible tobacco products. But there’s plenty of debate in the scientific community as to whether that’s actually true. For every study that suggests e-cigarettes can help smokers quit, there’s another that says they can’t.

Now, one of the most comprehensive studies yet provides solid support for daily vaping. It found that adult cigarette smokers who also used e-cigarettes every day were 77% more likely than non-users to have quit and stayed off cigarettes after two years.

The paper, published in the journal Nicotine & Tobacco Research, used data from about 8,200 adults who participated in the nationally representative Population Assessment of Tobacco and Health Study. Each person provided information about their health, lifestyle and tobacco use, then updated researchers about their tobacco use a year and two years later.

At the start of the study, only 3.6% of smokers reported daily e-cigarette use, while 18% reported more sporadic use. But people in that small group of daily vapers, the researchers found, were more likely than either periodic e-cigarette users or non-vapers to report abstaining from traditional cigarettes by the end of the study. Eleven percent of the original daily vapers reported being cigarette-free during both of the follow-up surveys, the researchers found—a relatively small portion overall, but a significant improvement over the 6% of non-vapers who had kicked the habit.

Sporadic e-cigarette use, the researchers found, was not associated with higher odds of quitting, perhaps because these people were not using e-cigarettes in hopes of completely ditching combustible cigarettes, or because they could not satisfy their nicotine cravings with less-consistent use. Past studies that did not find a connection between vaping and smoking cessation may not have accounted for the differences in daily versus periodic use, the authors theorize.

Some public-health experts also fear that a sustained nicotine habit, in the form of vaping, may increase a former smoker’s chances of relapse. One study published earlier this month found that to be true. But in the new study, daily vapers were only slightly more likely than non-users to revert back to cigarette smoking. About 4% of daily vapers who reported quitting after one year relapsed by the next year, compared to about 3% of non-vapers.

E-cigarettes contain fewer known cancer-causing chemicals than traditional cigarettes, but they aren’t risk-free. An accumulating body of research suggests they can cause heart and respiratory issues (although one prominent study on vaping and cardiovascular disease was later retracted), and those risks may compound when they’re used in tandem with cigarettes—a concerning prospect, since, as the new study shows, many smokers use both products. Nonetheless, the latest research offers some of the strongest evidence yet that e-cigarettes can play an important part in further reducing cigarette-smoking rates in the U.S.

This post was updated to reflect the retraction of prior research.

Write to Jamie Ducharme at jamie.ducharme@time.com.