More than 1.3 million people signed up for ObamaCare plans in the week leading up to a key December deadline, a demand that federal health officials have called "unprecedented."
Nearly 40 percent of those who signed up are new customers, a sign that uninsured people have paid attention to the Dec. 15 deadline to get insurance and avoid a penalty next year.
The surge in demand is forcing some customers to put their names down on a waiting list until the call center can help them enroll.
About 1 million consumers left their contact information with health officials to hold their place in line, HHS said.
The 1.3 million figure reflects data from Dec. 12. That means the busiest days of traffic were not counted in the tally.
At least 4.3 million people have now signed up for plans that would begin in 2016, though not all of those who submitted applications will ultimately pay premiums.
Hundreds of thousands of customers had already picked plans on Dec. 14 and 15, the two days before the deadline.
The early enrollment figures are far above the administration's goal of adding 900,000 new customers for the entire signup season, which lasts through Jan 31.