By Tami Luhby, CNN

(CNN) -- President Joe Biden is wasting no time establishing his vision for the Affordable Care Act and reversing many Trump-era measures aimed at weakening it.

In his first two months in office, Biden has taken several steps to bolster the landmark health reform law, which marks its 11th anniversary on Tuesday, and to embed it even more firmly in the nation's health care system. Former President Barack Obama is scheduled to speak Monday about how the Affordable Care Act has benefited Americans and how the Democrats' $1.9 trillion relief package, which Biden signed into law earlier this month, has strengthened the law.

Aided by the stimulus package, the Biden administration is making these moves even before its top health officials are in place. Health and Human Services Secretary Xavier Becerra was only confirmed on Thursday, while the President's pick to run the Centers for Medicare and Medicaid Services, Chiquita Brooks-LaSure, has yet to go before the Senate.

And these efforts come as the administration is also focused on ramping up the battle against Covid-19 and getting more Americans vaccinated.

Just over a week into his term, Biden signed an executive order directing federal agencies to re-examine a multitude of actions taken by former President Donald Trump, including policies that make it more difficult to enroll in Medicaid and the Affordable Care Act and that reduce affordability or financial assistance.

Biden also signed a presidential memorandum in late January to reverse restrictions on abortion access domestically and abroad imposed and expanded by Trump officials.

"The Biden administration is seizing the moment and taking steps to improve access during the pandemic but also setting the groundwork for other ways to continue to strengthen and protect both Medicaid and the ACA," said Allison Orris, a partner at Manatt Health, a professional services firm, and former Obama administration official.

These moves, however, were easy wins for Biden.

It will be much more difficult for him to enact his other major health care campaign promises, including creating a government-run public option to compete with private insurers, lowering the age to buy Medicare coverage to 60 and reducing drug prices. These mainly require the support of Congress, where Democrats hold only slim majorities in both houses -- and some in the party are still pushing for more dramatic changes, including enacting "Medicare for All."

Here's what Biden has done so far:

Opened up Obamacare enrollment

Uninsured Americans who want to buy Affordable Care Act coverage have until May 15 to do so, thanks to Biden's executive order.

The federal Obamacare exchange, healthcare.gov, reopened in mid-Feburary for a special enrollment period. Most states that operate their own marketplaces are also doing the same or are extending their sign-up season for several more weeks.

The President is hoping that some of the nearly 15 million uninsured people eligible for Affordable Care Act policies, the vast majority of whom qualify for financial assistance, will participate.

More than 206,000 people signed up for coverage on the federal exchange in the first two weeks of the special enrollment period, nearly triple the number during the same time frame last year, when access was more restricted. But it's unclear how many uninsured Americans will ultimately opt to purchase policies.

To raise awareness of the opportunity, the administration is pouring $50 million into marketing and outreach. It is also providing about $2.3 million to 30 navigator organizations that assist consumers in signing up for plans.

Trump last spring refused to open up a special enrollment period as the pandemic engulfed the nation. His administration also slashed funding for marketing and enrollment assistance during his term.

Beefed up Obamacare premium subsidies

More Americans can qualify for heftier federal help paying for Affordable Care Act policies for two years, under the Democrats' relief package. Providing more assistance was one of the key provisions of his campaign platform.

Enrollees will pay no more than 8.5% of their income towards coverage, down from nearly 10%. Also, those earning more than 400% of the federal poverty level -- about $51,000 for an individual and $104,800 for a family of four in 2021 -- are now eligible for help.

Lower-income enrollees can have their premiums eliminated completely for two years, and those collecting unemployment benefits can sign up for coverage with no premiums in 2021.

The stimulus-enhanced premium subsidies will be available on the federal exchange on April 1, but the administration is still working on making the zero-premium plans available for the jobless. States that run their own marketplaces have their own timelines. In California, for instance, uninsured residents will be able to access the more generous subsidies starting April 12, and those already in Obamacare plans will automatically receive them as of May 1.

The enhanced subsidies mean that most uninsured people eligible to buy Obamacare policies -- as well as the nearly 14 million consumers already insured on the individual market -- can pay less for coverage, according to a recent Kaiser Family Foundation analysis. Many could also afford to upgrade to plans with lower deductibles.

Separately, the relief package provides assistance to laid-off workers who want to remain on their employer health insurance plans through COBRA. They will not pay any premiums from April through the end of September, though the Biden administration has yet to announce when this provision will be available.

Defending the Affordable Care Act before the Supreme Court

The Biden administration last month told the Supreme Court that it should uphold the health reform law.

The Trump administration had sided with a coalition of Republican-led attorneys general seeking to strike down the law. At issue is whether Obamacare's individual mandate was rendered unconstitutional when Congress reduced the penalty for remaining uninsured to zero and, if so, whether that would bring down the entire law.

The justices heard oral arguments in the case in November and are expected to issue a decision by July.

Striking down the law would imperil the health coverage of millions of Americans and make it harder for Biden to fulfill his health care promises, many of which rely on Obamacare.

Overturning Medicaid work requirement approvals

The Biden administration took swift, though quiet, steps to reverse one of Trump's most controversial health care moves: Allowing states to require Medicaid recipients to work in order to receive coverage.

The Centers for Medicare & Medicaid Services last week sent letters to Arkansas and New Hampshire withdrawing work requirement approvals granted by the Trump administration.

The move follows a February notice to multiple states that the agency was deciding whether to withdraw the approvals. It noted that it has preliminarily determined that such a mandate would not promote the objectives of the Medicaid program -- a key factor in a legal case now before the Supreme Court.

The justices were set to hear oral arguments later this month on whether the federal government can allow states -- specifically Arkansas and New Hampshire -- to impose work requirements but recently removed the case from their calendar.

Some 12 states received approval to require certain enrollees to work, volunteer, take classes or search for jobs, typically for at least 80 hours a month. Seven additional states are awaiting approval. The mandate is not actually in effect anywhere, largely because of legal challenges.

About 18,000 people were stripped of their insurance in Arkansas -- the only state to fully implement the rules before being stopped by a federal judge -- within a few months of the mandate taking effect in 2018.