(New throughout, adds details and comments from Sebelius and analyst)
By David Morgan
WASHINGTON, Feb 12 (Reuters) - The Obama administration on Wednesday said the number of people who have enrolled in private Obamacare health plans rose to 3.3 million from Oct. 1 to Feb. 1, providing new evidence that its effort to extend coverage to the uninsured is gaining momentum.
Data collected from new health insurance marketplaces set up in all 50 states, under President Barack Obama's healthcare law, showed enrollment rising by 1.1 million or 53 percent in January and surpassing a government projection set before the botched rollout of the federal website HealthCare.gov.
The U.S. Department of Health and Human Services initially expected a January enrollment figure of just over 1 million.
"We're seeing a healthy growth in enrollment," Kathleen Sebelius, U.S. Health and Human Services Secretary, told reporters in a conference call. "The covered population is getting younger," she added. Healthcare analysts say Obamacare needs to attract a substantial proportion of younger, healthier enrollees to keep costs in line.
Administration officials said the enrollment results bring to 9.6 million the number of people who have signed up for private plans or been found eligible for the Medicaid program for the poor since enrollment began on Oct. 1.
The burgeoning enrollment numbers provided the administration with good news at a time when it is coming under mounting attack from Republicans, who hope to use Obamacare's unpopularity with voters to craft a winning campaign message for the November midterm election battle for control of Congress.
"They are definitely getting closer to the original expectations for enrollment, including likely some catch up from the disastrous first couple of months in the federal marketplace," said Larry Levitt, a health policy expert at the nonpartisan Kaiser Family Foundation.
But the numbers continue to lag on the crucial demographic of Americans 18 to 34 years of age. Enrollment from that relatively young and healthy group must be substantial to keep a lid on future cost increases by compensating for the higher costs of insuring older or sicker people.
The administration said the portion of young enrollees rose slightly to 25 percent of the total enrollment population for the Oct. 1 to Feb. 1 period. But that remained well below the 38 percent participation level initially projected by the White House.
Sebelius said enrollment among younger adults was strong. These new enrollees also tended to favor plans in the middle-to-higher quality range that includes silver, gold and platinum plans.
The new figures place the enrollment effort more than half way to a private insurance projection of 6 million enrollees for 2014, which the nonpartisan Congressional Budget Office issued last week. CBO scaled back its expectations from an initial 7 million due to the technical problems that overwhelmed the federal marketplace and several state exchanges in the early weeks of enrollment.
The data showed 1.4 million people enrolling through state-run marketplaces and 1.9 million through the exchanges that the federal government operates in 36 states.
Officials were unable to say how many enrollees have gained health coverage for the first time or switched into Obamacare plans from other coverage including plans that were canceled by insurers last year because they did not meet new quality standards.
About 82 percent of marketplace enrollees qualify for federal subsidies to help pay for premiums or out of pocket costs. (Reporting by David Morgan; Editing by David Storey and Peter Cooney)