Health Website Enrollment Is Close to Doubling Pace President Obama took responsibility last week for the troubled rollout of the online federal health insurance marketplace. WASHINGTON - The pace of enrollment in health plans through the troubled federal insurance marketplace has nearly doubled since the end of October as software engineers have resolved some 200 of the more than 600 initial defects that had rendered the site all but unusable, according to people familiar with the repair effort. As of mid-November, the number of enrollees, which the Obama administration defines as people who have selected a marketplace plan, was more than 50,000 - up from 27,000 in the entire month of October, but still a fraction of the number the administration once hoped for. Despite the progress, specialists are worried about whether they can meet the administration's goal of enabling four in five users to enroll through the online federal exchange, HealthCare.gov, by the end of the month. One person familiar with the effort said a more realistic goal was that four out of five people "have a positive experience," which could include being redirected to customer service agents. White House officials said on Monday that many of the remaining users would turn to call-in or counseling centers because their insurance situations were complicated. But specialists involved in the repair effort said technical issues may frustrate more users than administration officials suggest. And it is unclear how many fixes remain to be made, because the list keeps changing. Jay Carney, the White House press secretary, said the administration was still considering ways for people to sign up for health care coverage directly with insurance companies, working around the struggling website. Opponents of the 2010 health care law are already moving on to their next target. Two House committees will hold simultaneous hearings on Tuesday to press officials from the Health and Human Services Department and its computer contractors on security vulnerabilities. White House officials and some computer experts say much of the criticism is overblown, designed more to scare would-be enrollees away from the insurance exchanges than to prompt corrective action. But the concern is bipartisan. At a closed-door meeting last week, two Democratic senators pressed administration officials on efforts by Chinese hackers to break into the site, according to a Democratic Senate official at the meeting. "When consumers fill out their online marketplace applications, they can trust that the information that they are providing is protected by stringent security standards," said Patti Unruh, a spokeswoman for the health department's Centers for Medicare and Medicaid Services, which is responsible for the federal exchange. "Security testing happens on an ongoing basis using industry best practices to appropriately safeguard consumers" personal information." The running battle against the health care law has kept the White House and Democrats on their heels. As they work to respond to one set of problems, the law's opponents move onward. Republicans began with attacks on the website's functionality, shifted to millions of cancellation notices going to people whose insurance policies did not meet the law's coverage standards, and are now pressing the computer security case. On Friday, the House Committee on Oversight and Government Reform will hold a field hearing in the politically sensitive state of North Carolina on yet another front: rate shocks that Republicans insist are coming. The computer security question may be particularly delicate. The federal insurance website collects a broad range of personal information, including applicants" Social Security numbers, addresses, emails, income and health information. House Republicans have latched on to a final report by the Mitre Corporation, one of the main firms hired to assess the security of the site, which said on Oct. 11, 11 days after the site went live, that it was "unable to adequately test the confidentiality and integrity" of the health exchange "in full." Mitre went on to say that a "complete end-to-end testing" of the site "never occurred." Eric Lipton and Michael D. Shear contributed reporting.