Current e-cigarette use among high school students almost tripled between 2013 and 2014, from 4.5% to 13.4%.
The report's findings show that, for this first time since 2011 - when collection of data on electronic cigarette (e-cigarette) use began - the use of e-cigarettes among this population has exceeded use of all other tobacco products - including conventional cigarettes.
Dr. Tom Frieden, director of the Centers for Disease Control and Prevention (CDC), says the findings are "worrisome." He notes there are a number of concerns surrounding the use of e-cigarettes among youth.
"We're concerned that there are multiple aspects of e-cigarette use that are concerning that includes addiction to nicotine, effects on the developing brain, and the significant likelihood that a proportion of those who are using e-cigarettes will go on to use combustible cigarettes," he adds.
The report's findings were drawn from the 2014 National Youth Tobacco Survey - a questionnaire completed by a nationally representative sample of middle and high school students in the US, which gathers information on current tobacco use.
The survey collected such data between 2011 and 2014 from more than 22,000 students in grades 6-12 who attended public or private schools.
2 million middle and high school students currently using e-cigarettes
The survey revealed that between 2011 and 2014, current use of e-cigarettes - defined as using an e-cigarette at least once in the past 30 days - among middle and high school students increased significantly.
The biggest increase was seen between 2013 and 2014. Current e-cigarette use among high school students almost tripled in this 1 year, from 4.5% to 13.4% - a rise from 660,000 high school students using e-cigarettes in 2013 to 2 million in 2014. E-cigarette use also tripled among middle school students in this period, from 1.1% (120,000) in 2013 to 3.9% (450,000) in 2014.
The report also revealed an increase in current hookah smoking; it almost doubled in high students between 2013 and 2014, from 5.2% (770,000) to 9.4% (1.3 million), making hookah the most commonly used product after e-cigarettes last year. In middle school students, current hookah use increased from 1.1% (120,000) in 2013 to 2.5% (280,000) in 2014.
Between 2011 and 2014, there was no reduction in overall tobacco use. Overall rates of any tobacco use in 2014 stood at 24.6% for high school students and 7.7% for middle school students.
Though decreases were found in the use of conventional cigarettes, smokeless tobacco, cigars and pipes, the rise in e-cigarette and hookah use offset these reductions.
"It's very concerning," says Dr. Frieden. "It more than counterbalances the decrease in cigarette smoking, which we've seen occurring over the last few years. The decrease in cigarette smoking, of course, it's a good thing when fewer kids are smoking cigarettes. On the other hand, it would be a mistake to suggest there is a causal relationship between the increase in e-cigarette use and the decrease in child tobacco use."
Use of multiple tobacco products was found to be common last year. Among high school students, 12.7% reported using two or more, while 3.1% of middle school students reported using at least two tobacco products.
Findings 'underscore' need for FDA regulation of e-cigarettes
At present, the Food and Drug Administration (FDA) do not regulate e-cigarettes, though the organization is in the processing of finalizing a rule that will bring them under the same authority as other tobacco products.
According to Mitch Zeller, director of the Center for Tobacco Products at the FDA, the results of this survey emphasize the need to regulate e-cigarettes:
"In today's rapidly evolving tobacco marketplace, the surge in youth use of novel products like e-cigarettes forces us to confront the reality that the progress we have made in reducing youth cigarette smoking rates is being threatened.
These staggering increases in such a short time underscore why FDA intends to regulate these additional products to protect public health."
In addition, the CDC say the report highlights the need for tobacco control and prevention strategies for all tobacco products in youth - not just conventional cigarettes.
"Comprehensive programs work," says Dr. Frieden. "Smoke-free laws should apply to e-cigarettes as well. Hard-hitting ads about tobacco need to continue and we need to ensure that programs like minimum age requirements for purchase of e-cigarettes and comprehensive tobacco control programs are implemented at the state and local level."
"Nicotine addiction is often a lifelong challenge [that] usually starts in childhood," he continues. "The less likely someone is to use tobacco as a child, the less likely they are to use it as an adult."
Last month, Medical News Today reported on a study published in the journal Health Communication, in which researchers found vaping in e-cigarette advertisements may encourage current and former tobacco smokers to use conventional cigarettes.