Researchers at the University of California, San Diego School of Medicine believe e-cigarettes have helped fuel the increase.
Mr Hajek said: 'It's absolutely clear that e-cigarettes help smokers replace cigarettes'.
Christopher Bullen, professor of public health at the University of Auckland, said that any ill effects of e-cigarettes are 'likely to be rare compared with the harms of continuing to smoke.
But scientists remain divided over whether e-cigarettes are a "gateway" to smoking or a less harmful tool that helps smokers quit.
Overall, the number of people who quit smoking increased by 1.1 percentage points in 2015 from 2011.
The study claimed it used the largest representative sample of e-cigarette users among the USA population, and the impact was studied on a larger scale than previous studies.
E-cigarette users were identified from the most recent survey, while smoking quit rates were obtained from those who had reported smoking cigarettes 12 months before the survey.
The latest study that focused on e-cigarettes and vaping showed that those who used e-cigarettes were more likely to stop smoking altogether than those who didn't.
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And convenience store owners worry sales of other products will decrease if fewer customers are coming in to buy cigarettes.
Whilst this report used the largest representative sample of smokers and e-cigarette users available to date, it still has some weaknesses. It used surveys, which don't tend to offer the most detailed information, such as the type of e-cig used.
"All we can say is at a time when e-cigarette use is increasing, successful smoking cessation increased, and the prevalence of adults who smoked dropped", said Dr. Steven Schroeder.
"With proper regulation, we could increase the potential of e-cigarettes to reduce the horrific toll of cigarette smoking in our society", he added. "But if those don't work - try an e-cigarette".
"Other interventions that occurred concurrently, such as a national campaign showing evocative ads that highlight the serious health consequences of tobacco use and state tobacco control efforts, no doubt played a role", Zhu said in the release.
However, he emphasizes the current study gives e-cigs a strong case for contributing to an increase in Americans quitting smoking at the population level.
"If the 40 million smokers in the US switched to e-cigarettes, the nation would be a lot healthier for it", Schroeder said.
The survey was the fifth US Current Population Survey-Tobacco Use Supplement (CPS-TUS).
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