The number is a vast improvement over last year's launch.
More than 462,000 people selected a health plan on HealthCare.gov in the first week of open enrollment, the Health and Human Services Department announced Wednesday.
The number is a significant improvement from last year, when the federal enrollment website was essentially nonfunctional at launch. During the first two months of the first open-enrollment period in 2013, about 137,000 people chose a plan on the federal exchange.
This year, the website hasn't crashed, HHS said.
"It's still early, and we have a long way to go," said HHS Secretary Sylvia Mathews Burwell. "But we're off to a solid start."
The numbers announced Wednesday include only individuals using the federal marketplace, and do not include the 14 states that run their own exchanges.
The enrollments are about evenly split between new and returning users: 48 percent are new consumers, while 52 percent are consumers renewing coverage—either with the same plan or with a different exchange plan.
HHS is strongly urging former users to come back into the system and shop around, rather than allow their plan to auto-renew, which could stick consumers with premium spikes.
More than 1 million people have submitted applications for coverage, and more than 3.7 million have used HealthCare.gov. Nearly 96,000 have used CuidadoDeSalud.gov, the Spanish-language site.
HHS officials remain optimistic that they will hit their revised enrollment goal of 9.1 million next year.
The Centers for Medicare and Medicaid Services will continue to release a detailed monthly enrollment report, similar to last year, which will include enrollment numbers from both federal and state-based marketplaces. The agency also plans to release weekly "snapshot" reports, like the one on Wednesday, that give a broader "point-in-time estimate" of how enrollment is going.