Death rates from smoking related diseases can be decreased by 21 percent with the e-cigarettes in those born after 1997, according to a Nicotine & Tobacco Research. 

The National Institute on Drug Abuse, the National Cancer Institute and the Cancer Intervention and Surveillance Modelling Network, found that under most plausible scenarios e-cigarettes and other vapour products have a generally positive public health impact, says study. 

Earlier this year a University of California study of high school students found that those who used e-cigarettes were more than twice as likely to also smoke traditional cigarettes. 

Many experts believe there are health benefits for smokers who switch completely to e-cigarettes. 

David Abrams, executive director of the Schroeder Institute of Tobacco Research and Policy Studies at the Truth Initiative, said, "While the data are still not as clear as we would like, we present the entire picture with national data so we think our estimates are as good as we can get". 

"Those are not the people we are concerned with," David Levy, a professor of oncology at Georgetown Lombardi Comprehensive Cancer Center and the study's lead author said in an interview.

"We tried to get an idea of the number of people who progressed to established use."

FDA on may 5 announced a final rule extending its tobacco authority to include e-cigarettes, pipe tobacco, cigars and hookah.