Nearly 3.3 million people enrolled in the Health Insurance Marketplace plans by Feb. 1, with January alone accounting for 1.1 million plan selections in state and federal marketplaces.
Preliminary figures for February indicated about 700,000 signed up for private health insurance in February, but a government official said a full enrollment report for February would be released in mid-March.
The numbers do not include the millions who have signed up for expanded Medicaid.
"Our outreach efforts are in full force with community partners and local officials participating in hundreds of events each week and enrollment assistors are helping more and more people enroll in coverage," Marilyn Tavenner, administrator of the Centers for Medicare & Medicaid Services, part of HHS, said in a statement.
"Consumers are shopping and enrolling in plans on HealthCare.gov every day; system error rates are low and response times are consistently less than half a second. Our call center has handled more than 12 million calls so far and is open 24/7."
However, Kathleen Sebelius, secretary of the HHS, walked back the Obama administration from its unofficial goal of 7 million Affordable Care Act signups by the end of open enrollment for this year on March 31.
In a Tuesday appearance on HuffPost Live to discuss Affordable Care Act outreach to African-American communities, Sebelius said the administration might not reach 7 million mark but will most likely enroll 5 million to 6 million U.S. adults for private health insurance.
"First of all, 7 million was not the administration," Sebelius said told the Huffington Post. "That was a CBO -- Congressional Budget Office -- prediction when the bill was first signed. I'm not sure where they even got their numbers," Sebelius told the website the Huffington Post.
"I'm more interested in what we're doing today, getting the word out to target populations. Never before has affordable healthcare been available to people who didn't have healthcare in their workplace."