AMID THE nationwide furor over the Senate draft health-care bill, a public-health victory has gone mostly unnoticed. According to a new report from the Centers for Disease Control and Prevention, the estimated number of middle and high school students who are tobacco users dropped from 4.7 million in 2015 to 3.9 million in 2016. This was largely driven by a reduction in the number of teenagers using e-cigarettes, which are less harmful than regular cigarettes but still contain nicotine. The downturn is a success for advocates and officials who have worked to curb teen tobacco use — but it should not be heralded as the end of the road.

Teenage smoking has long been one of the most serious public-health issues. Smoking is the leading cause of preventable death in the United States, and 9 in 10 American smokers had their first taste of tobacco before the age of 18. Although policies to curb teen smoking showed signs of success for a time, youth tobacco rates remained stagnant between 2011 and 2015. During this period, the use of e-cigarettes among high school students increased by a staggering 900 percent.

With these statistics in mind, the recent decline in teen tobacco and e-cigarette use is an encouraging signal that interventions may be working. It is difficult to determine causation, but experts have attributed the drop to a range of federal, state and local policies designed to dissuade young adults from using tobacco, such as increasing tobacco taxes and expanding antismoking ordinances to include e-cigarettes and other new products. States have run targeted media campaigns that work alongside federal efforts, such as the Food and Drug Administration’s “Real Cost” campaign and the CDC’s “Tips from Former Smokers.” The CDC report suggests that at least some of these strategies have been effective.

But the report also highlights challenges that lie ahead. Millions of teenagers across the country are still using tobacco in some form, and the introduction of new tobacco products could drive up rates. There are also significant disparities among states and communities: Rural, low-income, and lesbian, gay, bisexual and transgender youth are particularly at risk due to targeted marketing and policy variation between different jurisdictions. This makes federal regulation by the FDA all the more important.

The FDA, however, has delayed the enforcement of new regulations on e-cigarettes and cigars. Delays are commonplace in new administrations, but it is important that the agency take up these stricter standards after the three-month postponement. It would be a pity if these long-awaited signs of progress were undercut because the FDA declined to do its job.