The move comes just a week after the close of the rocky enrollment period for President Barack Obama's health care law. Website failures marred the opening weeks of the six-month enrollment period, but the administration rebounded strongly by enrolling more than 7 million people in health insurance plans.
Sebelius' resignation could set the stage for a contentious election-year confirmation hearing for whomever Obama nominates to replace her. Sebelius has served as HHS secretary since the start of the Obama administration.
Earlier Thursday, the HHS department announced enrollment for the president's health care law has grown to 7.5 million Americans, the Obama administration announced Thursday, handing President Barack Obama and the Democrats bigger coverage numbers to tout in the face of election-year attacks.
Sign-ups for the law stood at 7.1 million last week, but people who had started signing up when the enrollment period closed March 31, or who had trouble signing up, were given extra time to finalize their applications. Four hundred thousand more have now done so, Health and Human Services Secretary Kathleen Sebelius said in testimony before the Senate Finance Committee. Sebelius said she expects the figure to continue to grow.
The original number already exceeded expectations, a surprise success after a disastrous roll-out and welcome news for Democrats who've been forced to defend their support for the unpopular law derided by critics as "Obamacare."
The Blue Cross Blue Shield Association says that 80 percent to 85 percent of the people who had enrolled with Blues plans through the health insurance exchanges had paid their premiums as of Feb. 1, which would represent a significant reduction over the administration's raw numbers.
People who started signing up during open enrollment but didn't finish have until April 15 to finish signing up for coverage, while people who encountered any one of a number of problems that might have kept them from signing up are eligible for a so-called "special enrollment period" that would bring another 60 days to sign up.
The 7.5 million represents people who've sought insurance from private companies through new on-line marketplaces created by the law. The law also includes an expansion of Medicaid, and 3 million more Americans have obtained insurance that way, the administration has said.
People who are eligible for the law's Medicaid expansion can sign up at any time of the year, but with limited exceptions, insurance companies have stopped selling individual policies outside the new government-sponsored health care markets until the next open enrollment season, which starts Nov. 15.