Health and Human Services Secretary Kathleen Sebelius in a December visit to the Miami-Dade library.

Young adults are increasingly signing up for Obamacare health insurance plans, officials said Wednesday as they revealed that nearly 3.3 million people of all ages had enrolled as of Feb. 1.

"It's very encouraging news," said US Health and Human Services Secretary Kathleen Sebelius about the overall enrollment data, which represents a 53 percent increase in total signups since the end of December, when nearly 2 2 million had enrolled.