March 11 (Bloomberg) -- About 4.2 million people signed up for Obamacare health plans through February as the administration tries to focus the attention of consumers on the March 31 deadline for Americans to enroll.

Youth enrollment continued to expand, with 1.1 million people ages 18 to 34 signed up by March 1, an increase of 268,475 in a month, U.S. health officials said today in a report. President Barack Obama has made a special effort to appeal to young adults, including exchanging barbs with comedian Zach Galifianakis while pitching the health-care law on the actor’s parody web talk-show “Between Two Ferns.”

A survey this week found the number of uninsured dropped since the health-care law took effect Jan. 1. About 15.9 percent of Americans lack coverage this year, down from an all-time high of 18 percent in 2013, Gallup Inc. said yesterday.