Updated July 29, 2021 at 6:18 PM ET

With the highly transmissible delta variant driving a surge in coronavirus cases, President Biden on Thursday sought to boost a flagging vaccination campaign by announcing new efforts, including rules for federal employees and contractors.

"Vaccines are the best defense against you getting severely ill from COVID-19 — the very best defense," Biden said in remarks from the White House.

The president has been trying to expand access to COVID-19 vaccines and pleading with Americans to get inoculated, but he has limited ability to force action.

Except when it comes to the federal workforce. Here, Biden has the ability to go beyond urging.

Under new rules laid out Thursday, federal employees and contractors — a group that the White House said includes more than 4 million Americans — will need to confirm they are vaccinated or be tested once or twice a week for the virus. Those who cannot attest to being vaccinated will also have to wear masks while on the job.

The federal government is the largest employer in the nation, and the move could spur private companies to take similar steps. Some already have. The administration plans to urge businesses to follow the federal government's model.

Biden is also directing the Defense Department to look into how and when to add the COVID-19 vaccine to the list of required vaccinations for the military.

Responding to a reporter inquiry after his remarks, Biden added it's "still a question" whether the federal government could mandate vaccines for the whole country.

The White House is also aiming to incentivize inoculation by encouraging state and local governments to offer $100 to people who get fully vaccinated. Biden said state and local governments could use funds from the American Rescue Plan for payments, and that the Kroger grocery store chain saw vaccination rates jump when it offered $100.

"I know that paying people to get vaccinated might sound unfair to folks who've gotten vaccinated already," Biden said, "but here's the deal: If incentives help us beat this virus, I think we should use them. We all benefit when we get more people vaccinated."

The president said the federal government will also reimburse small and medium-size businesses to give their employees paid time off to get themselves and their family members vaccinated.

"We're still hearing that people are unable to get time off from their employer to get vaccinated. This is unacceptable," he said. "Employers, this costs you nothing. If you haven't given employees paid time off, do it now, please."

"This is an American tragedy"

In his remarks, Biden spoke about the delta variant and emphasized that the vast majority of new hospitalizations and deaths are among the unvaccinated.

"Last month, the studies showed that over 99% of COVID-19 deaths had been among the unvaccinated," he said.

"This is an American tragedy," he added. "If you're out there unvaccinated, you don't have to die."

Biden acknowledged the difficulty his administration faced in trying to assure Americans of the vaccines' safety and efficacy, and in tamping down misinformation. He said politics shouldn't play a role in people's decisions. Surveys have shown that Republicans are far less likely to be vaccinated than Democrats.

"The vaccine was developed and authorized under a Republican administration. And it has been distributed and administered under a Democratic administration," he said. "The vaccines are safe and highly effective. There's nothing political about them."

He said the same of masks: "A mask is not a political statement. It's about protecting yourself and protecting others."

He notably praised Senate Minority Leader Mitch McConnell of Kentucky and Alabama Gov. Kay Ivey, both Republicans, for encouraging their constituents to get the vaccine.

Changing mask guidance

The remarks and the steps from Biden come two days after the Centers for Disease Control and Prevention changed its mask guidance for Americans, urging even people who are vaccinated to wear masks indoors in places with high virus transmission.

It's a big shift from the Fourth of July celebration Biden held to mark a measure of "independence" from the virus. At the time, he lauded fresh efforts to reopen the country.

Back in May, when the CDC abruptly lifted its universal mask mandate, Biden called it a "great day." His administration eagerly embraced the relaxed guidance with big indoor, maskless events.

The back and forth from the CDC amounts to whiplash and struck many as arbitrary.

"They got a good grade, probably an A in terms of biological science, when they came out with some of those recommendations, but they got an incomplete at best on behavioral science," said Saad Omer, director of the Yale Institute for Global Health.

Political implications

It's unclear how the CDC's actions could affect Biden politically, but the president has tied his own messaging to the agency and regularly stressed the idea of following "the science" rather than exerting political influence over big decisions.

Generally, Biden gets fairly high marks for his handling of the pandemic. The numbers of cases and deaths are way down, compared with when Biden took office in January. And the White House boasts of 80% of the nation's older people and 60% of American adults being fully vaccinated.

But more than 600,000 Americans have died from the virus, and much of the nation has grown tired of masks and more than a year of coronavirus restrictions.

And as next year's midterms close in, there's less room for error.

Democratic pollster Cornell Belcher notes that the current pandemic wave is driven by areas with low vaccination rates.

"If you could connect that back to Biden and his action or inaction, I think that's problematic. But I don't think you can," Belcher said. "I think it's hard to connect the dots around what's happening with the unvaccinated, particularly in the red states."

Still, it will be important for Biden to make sure schools open in the fall and the economy continues to improve. Democratic consultant Karen Finney, who has experience with crisis communications, said the White House has to keep being transparent about what's happening with the pandemic as conditions change, while not letting that overtake the rest of Biden's agenda.

"Keep moving on the things you can control. Keep moving on making sure that the campaign promises are met," Finney said.

As far as what the administration can control, the federal workforce certainly falls in that category.

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