By Tony Pugh, McClatchy Washington Bureau

WASHINGTON — Roughly 700,000 of the more than 8 million people who enrolled in marketplace health insurance plans have lost their coverage, Medicare administrator Marilyn Tavenner testified Thursday before Congress.

Her surprise disclosure came during a House Oversight and Government Reform Committee hearing in which Republicans blasted Tavenner about a lack of transparency and ongoing data security problems with the HealthCare.gov website created under the Affordable Care Act.

After a disastrous rollout that saw the federal insurance marketplace crash only minutes after its Oct. 1 debut, HealthCare.gov underwent a massive repair job by a team of private-sector computer experts from Silicon Valley.

By Thanksgiving 2013, the website was functioning properly and more than 8 million people signed up during an extended enrollment period that ended in May. Since then, Tavenner and other officials at the Department of Health and Human Services have been unable to say how many of the new enrollees have lost coverage because of non-payment.

After mentioning in Thursday’s testimony that 7.3 million Americans were covered by marketplace plans, committee chairman Darrell Issa (R-CA) asked Tavenner what happened to the other 700,000.

“Individuals may have either gotten employer-sponsored insurance, they may have found that they were eligible for Medicaid instead of the marketplace, and some individuals may have decided not to go forward and pay,” said Tavenner, who heads HHS’ Centers for Medicare and Medicaid Services.

When asked by Issa how many of the 700,000 were dropped because they didn’t pay their premiums, Tavenner said she didn’t know and added, “I don’t think you’ll know that until the end of the year.”

Even with the loss of nearly 10 percent of enrollees, Tavenner said she was pleased with what appears to be a 90 percent retention rate for marketplace sign-ups thus far.

“This is a brand new program. This has never been done before,” Tavenner testified. “I expect in some cases (some of the 700,000) may have moved. They may have gotten married. They may have gotten insured. They may have lost their income and gone on Medicaid or into the uninsured ranks. We will only know that as we look back. And we’re careful not to look back too early.”

Earlier this week, the Government Accountability Office released a report that criticized her department for information security and privacy weaknesses that compromise the personal information of HealthCare.gov users.

In testimony Thursday, Gregory Wilshusen, GAO’s director of information security issues, said HHS officials were slow to release documents and unnecessarily restricted GAO’s access to others, citing concerns about the security of the information.

The GAO report said the Centers for Medicare and Medicaid Services accepted increased security risks by allowing HealthCare.gov to launch on Oct. 1 when the system had not been fully tested. The investigative arm of Congress, the GAO also found problems in HealthCare.gov’s technical controls that protect the confidentiality, integrity and availability of data maintained in the system.

“CMS has not fully addressed security and privacy management weaknesses, including having incomplete security plans and privacy documentation, conducting incomplete security tests, and not establishing an alternate processing site to avoid major service disruptions,” the report said.

“Until these weaknesses are addressed, increased and unnecessary risks remain of unauthorized access, disclosure, or modification of the information collected and maintained by HealthCare.gov and related systems or the disruption of service provided by the systems,” the GAO report found.

The GAO report recommended 22 improvements to resolve technical weaknesses in security controls and six others to improve security and privacy controls.

Tavenner said the Centers for Medicare and Medicaid Services has implemented 19 of the 22 GAO recommendations so far and will comply with each of its six recommendations before the 2015 open enrollment period begins on Nov. 15.

She also said “end-to-end” testing of the entire federal marketplace will occur later this month or in October.

AFP Photo/Joe Raedle