Even as Congress has begun the process to repeal Obamacare, Americans continue to seek coverage through its insurance exchanges.

More than 11.5 million people have signed up for coverage through the federal marketplace, healthcare.gov, and the 12 state-based exchanges, as of Dec. 24, according to federal data released Tuesday. That's 286,000 more than the comparable time a year ago.

The number of people opting for Obamacare is under more scrutiny than usual this year, since President-elect Trump and Congressional Republicans have vowed to repeal it soon after he takes office on Jan. 20. Initial efforts, however, are already running into resistance, with some GOP members wanting to wait until a replacement plan is ready before voting to repeal.

Though the Trump administration takes control late next week, current Health & Human Services officials laid out a plan to further boost sign ups through Jan. 31, which marks the end of open enrollment. The agency is airing television and radio ads, sending targeted emails to potential customers and reaching out via YouTube and other social media channels -- continuing outreach efforts that have been underway during this enrollment season.

The Internal Revenue Service is also contacting those who paid a penalty for remaining uninsured. The agency recently announced that about 6.5 million Americans had to pay the penalty, typically $330, in 2015. That's less than the roughly 8 million who were penalized in 2014.

High on the list of targets is younger Americans, who typically are healthier and have lower health care expenses. However, they still make up only 26% of those signing up on the federal exchange to date, the same as last year.

It's unclear whether the marketing efforts will continue under Trump, who has vowed to repeal President Obama's signature health reform law.

Still, Obama and his officials continue to make a case for Obamacare.

"In access, quality and affordability, the Affordable Care Act has helped us make real progress for families across the nation," said Health Secretary Sylvia Burwell on Monday.

The Obama administration expects a total of 13.8 million people to sign up for plans by the end of the enrollment period, which began Nov. 1. However, it's common for people to drop their policies during the course of the year because they find coverage elsewhere, either through a job or a spouse. So, an average of 11.4 million people are expected to be in Obamacare policies during 2017.

Consumers aren't officially enrolled until they pay their first month's premium.

Related: GOP worried about Obamacare plan

Even before the election, there were concerns that prospective enrollees would be deterred by price hikes -- the average premium for the benchmark silver plan soared 22% for 2017 -- and the fact that some insurers had pulled out of the exchanges.

Most enrollees, however, are shielded from those increases by federal subsidies. Some 82% of people who have signed up for 2017 plans are eligible for subsidies, according to Health & Human Services Department officials. The average subsidy for those enrolling on the federal exchange is $4,600 a year.

Consumers are also shopping around for coverage. Some 56% of returning customers actively selected plan, up from 51% a year ago. Those who opt not to shop are automatically re-enrolled in their existing policy.