President Joe Biden kicked off a more urgent campaign for Americans to get COVID-19 booster shots Thursday, unveiling his winter plans for combating the coronavirus and its omicron variant with enhanced availability of shots and vaccines but without major new restrictions.

The White House released details of Biden's plan early Thursday.

In a speech from the National Institutes of Health on Thursday, Biden said his winter push focuses on five key policy efforts, but stressed that it “doesn't include shutdowns or lockdowns.” Instead, the campaign will focus on: 

• Expanding the nationwide booster campaign with more outreach 

• Launching new family vaccination clinics 

• Making free, at-home tests available and covered by private insurance

• Increasing surge response teams in communities with rising cases 

• Accelerating efforts to vaccinate countries around the world 

“My plan I'm announcing today pulls no punches in the fight against COVID-19. It’s a plan that I think should unite us,” Biden said. 

“Now, as we move into the winter and face the challenges of this new variant, this is a moment we can put the divisiveness behind us, I hope,” Biden continued, adding: “We can do what we haven't been able to do enough of through this whole pandemic: Get the nation to come together, unite the nation in a common purpose.”

The plan includes a requirement for private insurers to cover the cost of at-home COVID-19 tests and a tightening of testing requirements for people entering the U.S. regardless of their vaccination status. But as some other nations close their borders or reimpose lockdowns, officials said Biden was not moving to impose additional restrictions beyond his recommendation that Americans wear masks indoors in public settings.

The Biden administration has come to view widespread adoption of booster shots as its most effective tool for combating COVID-19 this winter. Medical experts say boosters provide enhanced and more enduring protection against COVID-19, including new variants.

Much remains unknown about the omicron variant, including whether it is more contagious, whether it makes people more seriously ill and whether it can thwart the vaccines.

About 100 million Americans are eligible for boosters under current U.S. policy, with more becoming eligible every day. Convincing those who have already been vaccinated to get another dose, officials believe, will be far easier than vaccinating the roughly 43 million adult Americans who haven't gotten a shot despite widespread public pressure campaigns to roll up their sleeves.

And while Biden's vaccination-or-testing requirement for workers at larger employers has been held up by legal challenges, the president on Thursday renewed his call for businesses to move ahead and impose their own mandates on workers so they can stay open without outbreaks.

Biden also announced that his administration will offer paid time off for federal workers to get their booster shot, saying: “While my existing federal vaccination requirements have been reviewed by the courts, this plan does not expand or add those mandates.”

In an effort to encourage more people to take the booster doses, the Biden administration is stepping up direct outreach to seniors — the population most vulnerable to the virus. The Centers for Medicare & Medicaid Services will send a notice to all 63 million Medicare beneficiaries encouraging them to get booster doses, the White House said. The AARP will work with the administration on education campaigns for seniors.

So far roughly 42 million Americans, about half of them seniors, have received a booster dose. The Centers for Disease Control and Prevention this week strengthened its booster dose recommendation to say all adults should get their boosters — rather than may get them — starting six months after their second dose of the mRNA vaccines from Pfizer or Moderna or two months after their Johnson & Johnson shot. 

Biden also announced Thursday an increase in mobile family clinics, where adults can get their booster shots as kids receive their initial vaccine, another move to improve access in the face of omicron.

"We hope that more people will take this seriously and get boosted," White House press secretary Jen Psaki said earlier in the day. "It's about making sure we're reaching more pharmacies, that we are making sure they have the supply needed."

The White House said the CDC was also developing new guidance for schools in an effort to reduce or eliminate current quarantine requirements for those who are not fully vaccinated and exposed to the virus. The new policies, which the White House said will be released in the coming weeks, could include so-called "test-to-stay" policies, in which those who are considered close contacts can continue to go to school but wear masks and undergo serial testing, in a bid to minimize learning loss and disruption. 

The administration's upcoming rule to require private insurers to cover at-home testing is still being drafted, and many details remain to be worked out, including under what criteria they will be reimbursable, officials said. 

Those insured by Medicare and Medicaid would not be eligible, but the White House said as many as 150 million people with private insurance would see easier and cheaper access to the at-home tests. The administration said it is making 50 million COVID-19 tests free for older people and other vulnerable groups for pickup at senior centers and community sites.

Asked why the administration did not go further and make more tests free to the general public or even ship tests directly to Americans, the White House spokeswoman pointed to an increase in supply in recent months.

"There are four times more tests available now than there were in the summer. We will continue to build on that," Psaki said. "Nothing is off the table."

Biden added that Americans will “be able to test for free in the comfort of home and have some peace of mind.”

Beginning next week, the White House said, all travelers to the U.S., regardless of nationality or vaccination status, will need to provide proof of a negative COVID-19 test within one day of boarding their flights. That's down from three days right now for those who have been vaccinated, in an added precaution against the omicron variant. But the White House has shelved tougher options, like requiring post-arrival testing or requiring quarantines upon arrival in the U.S.

Biden is also extending his directive requiring masks on airplanes and other public transit, which had been set to expire in January, through at least the middle of March, the White House said.

The administration is also informing states that it has more than 60 teams available to help them or their municipalities address surges in cases and public health shortages heading into the winter, with half aimed at bolstering hospital services and 20 targeted at supporting life-saving monoclonal antibody treatments.

As for vaccinating the rest of the world, Biden pledged an additional 200 million vaccines will be sent out to various countries over the next 100 days. 

“Let me be clear.: Not a single vaccine dose America ever sends to the rest of the world will ever come at the expense of any American,” Biden said, adding that vaccinating populations in other countries is the best way to stop the spread of the omicron variant across borders. “I'll always make sure that our people are protected first.”