(NBC News) - Fewer teenagers are smoking cigarettes than ever before.
Just 11 percent of high school students said they currently smoked in 2015, the Centers for Disease Control and Prevention said Thursday. That number stood at 15.7 percent in 2013 and 18.1 percent in 2011.
And just under a third of the students asked said they had ever tried a cigarette, the CDC found in its annual survey of risky behavior among U.S. children and teenagers. There's lots of good news in the survey, which shows many risk-taking behaviors, such as early sex and smoking, are down.
But teenagers more than replaced traditional cigarettes with e-cigarettes, a trend that worries the CDC.
The annual CDC survey found that 24 percent of high school students reported using e-cigarettes during the past 30 days. It's the first time that question has been asked on this particular survey, so there's no way to know if that's changed from years before.
"Current cigarette smoking is at an all-time low, which is great news. However, it's troubling to see that students are engaging in new risk behaviors, such as using e-cigarettes," CDC Director Dr. Tom Frieden said in a statement.
"We must continue to invest in programs that help reduce all forms of tobacco use, including e-cigarettes, among youth."
In 1991, the first time CDC asked teenagers about smoking, 27 percent said they smoked.
Anti-smoking advocates welcomed the news.
"It's troubling to see that students are engaging in new risk behaviors, such as using e-cigarettes."
"A lot of hard work at the national, state and local levels went into reaching this milestone, including running mass media campaigns and putting in place higher tobacco taxes, stronger smoke-free laws and other tobacco prevention policies that help protect the heart health of every American," said American Heart Association CEO Nancy Brown.
"The dramatic decline in youth smoking is a public health success story of extraordinary importance because cigarette smoking is the leading cause of preventable death in our country and kills nearly half a million Americans every year," added Matthew Myers, president of the Campaign for Tobacco-Free Kids.
"While the fight against tobacco is far from over, the huge drop in youth cigarette smoking leaves no doubt we can win this fight by fully implementing what we know works," Myers added.
For instance, he said, smoking rates started falling when the federal cigarette tax was increased by 62 cents in 2009.
"However, this survey also raises fresh concerns that other tobacco products, especially electronic cigarettes and cigars, are undermining overall efforts to reduce youth tobacco use and could be luring a new generation of kids into nicotine addiction," Myers added.
"All tobacco products are dangerous, and their ongoing use is a major risk factor for cardiovascular disease. We must shore up our efforts to stop this disturbing trend before it climbs higher and turns more young people into lifelong tobacco addicts."
"It isn't surprising that these unregulated products would be the ones that end up being used by youth, given they're easier to obtain and their access is largely unrestricted."
Robin Koval, CEO and president of the Truth Initiative, a group funded out of a tobacco company settlement with states to help fight smoking, said the shift to e-cigarettes shows the Food and Drug Administration needs to regulate them firmly.
The FDA released its final rules for e-cigarettes last month, but they'll take effect gradually.
"It isn't surprising that these unregulated products would be the ones that end up being used by youth, given they're easier to obtain and their access is largely unrestricted," Koval said.
"The new data are coming out just as lawsuits and other misguided efforts are unfolding in an attempt to prevent the FDA from moving ahead with their new limits on e-cigarettes. The numbers, however, make very clear why the FDA must be able to limit the marketing and appeal of these products to young people and review new products for their potential impact on public health without delay."
Other findings in the CDC report:
Fewer high school kids are having sex - just 41 percent, down from 47 percent for most of the last decade.
Fewer are drinking alcohol. About 63 percent had ever had a drink, compared to 66 percent in 2013 and 75 percent in 2007. Just under a third of high school students say they'd had at least one alcoholic drink in the past month, down from 35 percent in the last survey and down from 45 percent in 2007.
About 41 percent of drivers admitted to texting or e-mailing while driving, a trend that has not changed in recent years.
Just over 38 percent of teens said they had ever tried marijuana. That's up slightly from 31 percent in 1991.
About 17 percent of the students said they had taken prescription drugs such as Oxycontin, Vicodin, Adderall or Ritalin without a prescription.
More than 81 percent rarely or never wore a bicycle helmet.
Just under 18 percent of students said they had seriously considered attempting suicide in the past year.