Defense Secretary Lloyd Austin will seek a mandate to require that all service members get a coronavirus vaccine by mid-September, and could move that date up even sooner if a vaccine receives full approval from the Food and Drug Administration, according to defense officials and a new memo released by the Pentagon.

The effort to pursue a mandate is an acknowledgment of rising coronavirus rates across the country as the delta variant of the virus spreads, and the way in which covid-19 can wreak chaos in military units. It comes after months of senior defense officials cajoling service members to consult with their doctors and get the vaccine.

The Biden administration has directed agencies throughout the federal government to devise plans for requiring workers to get vaccinated.

“The intervening few weeks will be spent preparing for this transition,” Austin said in the memo. “I have every confidence that Service leadership and your commanders will implement this new vaccination program with professionalism, skill, and compassion. We will have more to say about this as implementation plans are fully developed.”

President Biden, who must approve Austin’s request for a mandate, quickly praised the decision as millions of Americans remain resistant to vaccines, and governments and employers increasingly turn to mandates.

“We cannot let up in the fight against COVID-19, especially with the Delta variant spreading rapidly through unvaccinated populations,” he said. “We are still on a wartime footing, and every American who is eligible should take immediate steps to get vaccinated right away.”

John Kirby, a Pentagon spokesman, said in a news briefing with reporters on Monday that if the FDA grants full approval for a coronavirus vaccine before September, Austin will have authority to require that version of the vaccine immediately, without presidential involvement. The FDA’s top vaccine official said last month that the agency is redeploying staff and adding technical resources to grant the Pfizer-BioNTech coronavirus vaccine full approval as quickly as possible.

Here are some significant developments:

  • After weeks of protests, France saw little drama on Monday as it expanded its national experiment with coronavirus mandates and began to require that people show a health pass to sit at cafes, eat at restaurants and access many other venues.
  • The CDC and the State Department and on Monday announced a slew of new travel warnings — some of them for countries previously praised for their response to the coronavirus. Thailand, Iceland, France, French Polynesia, Eswatini and Aruba were all added to a “do not travel” list citing high levels of covid-19.
  • Florida and Louisiana reported covid-19 hospitalizations at all-time highs on Sunday, as current virus hospitalizations nationwide have soared past 68,000 — well past the peak of last summer’s Sun Belt surge.
  • Dallas city school officials said they will require students and staff to wear masks in school buildings, defying an executive order by Texas Gov. Greg Abbott (R) barring local governments from issuing mask or vaccine mandates.
  • Washington state, where infections are rising, will require most state employees and all nursing home staff to get vaccinated against the coronavirus by October, Gov. Jay Inslee (D) said Monday. Other states have made similar moves.

In the next few weeks, the services will be required to put together a plan to get required vaccines moving, Kirby said.

“The services have a fair, but limited, amount of time to come back to the secretary with their implementation plans for how they would go out mandatory vaccines for all their personnel,” Kirby said.

In the next few weeks, the Pentagon also will move forward with planning for service members who are unvaccinated, Kirby said. He said he did not have the details on Monday and expected more information to be made available in coming days.

“Getting vaccinated against covid-19 is a key force protection and readiness issue,” Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff, added in a Monday letter that noted vaccination mandates are not new to the military.

Austin left open the possibility that he could speed up the vaccination requirement even sooner if coronavirus cases continue to rise.

“I will not hesitate to act sooner or recommend a different course to the President if I feel the need to do so,” the memo said.

As of Monday, about 66 percent of more than 1.3 million active-duty troops are fully vaccinated, according to data provided to The Washington Post.

But those numbers vary by service. The Marine Corps, which trends younger than the other services, has about 59 percent of its active-duty personnel vaccinated, said Maj. Jim Stenger, a service spokesman. The Navy, which deploys in tight quarters on ships, has about 75 percent of its active-duty members vaccinated, said Lt. Cmdr. Patricia Kreuzberger, a service spokeswoman.

With just over half the American population fully vaccinated, rising cases and hospitalizations are fueling new debates over covid-related mandates.

In Texas, where new infections and hospital admissions have been rising sharply, local leaders are clashing with Abbott over school mask rules as students return. Dallas city school officials said Monday that students and staff must wear masks in school buildings, defying Abbott’s executive order barring local governments from issuing mask or vaccine mandates, including in public schools.

In Florida, where covid-19 hospitalizations have hit an all-time high, Gov. Ron DeSantis (R) is facing pushback over his adamant opposition to mandates that he has called threats to “free society.” Florida education officials recently moved to give students access to a state voucher program that helps pay for private tuition if their public schools require masks — an acknowledgment that some schools in the state are requiring masks despite the state’s ban on such mandates.

DeSantis’s ban on vaccine passports was temporarily blocked by a federal judge late Sunday, paving the way for a cruise company to require vaccinations as DeSantis’s office vowed to appeal.

“A prohibition on vaccine passports does not even implicate, let alone violate, anyone’s speech rights, and it furthers the substantial, local interest of preventing discrimination among customers based on private health information,” DeSantis’s office said in a statement.

Coronavirus protocols in schools are under particular scrutiny as millions of children, many of them ineligible for vaccination, head back to the classroom. Young people 12 and over, who are eligible for the shots, lag behind adults in getting immunized. The Centers for Disease Control and Prevention has recommended that people resume wearing masks indoors in hot spots, as recent data suggests vaccinated people can in rare cases spread the virus.

The head of the country’s second-largest teachers union on Sunday shifted course to signal support for vaccine mandates for teachers.

Randi Weingarten, president of the 1.7 million-member American Federation of Teachers, said on NBC’s “Meet the Press” that “we need to be working with our employers, not opposing them, on vaccine mandates.” The union this week will “reconsider” its stance that supported only voluntary vaccinations, she said.

In the United States and beyond, another debate is playing out over the value of booster shots beyond a normal one- or two-dose coronavirus vaccine regimen.

German pharmaceutical company BioNTech on Monday reiterated its push for boosters, even as it said its coronavirus vaccine developed with Pfizer appears to be effective against the delta variant, echoing fellow vaccine maker Moderna. BioNTech said it also plans to test an updated vaccine targeted at delta.

On Sunday, America’s top infectious-disease expert, Anthony S. Fauci, said the United States would probably soon begin administering booster coronavirus vaccine shots to Americans with compromised immune systems. Countries such as Germany, France and Israel have pledged to give booster shots to some citizens more vulnerable to the coronavirus.

“People who have [transplants], people who are on cancer chemotherapy, people who have immune mediated diseases that require immunosuppression. … We need to look at them in a different light,” Fauci said on CNN. “We will almost certainly be boosting those people before we boost the general population that’s been vaccinated.”

He gave no definitive time frame but added: “We should be doing that reasonably soon.”

For generally healthy people who have been vaccinated, Fauci said that health experts would continue monitoring “very carefully” how well vaccine protections last before making any final decision on booster shots. The World Health Organization last week called for a moratorium on booster shots through at least September as poorer nations struggle to give first shots to even small fractions of their populations.

In a move that has gained national attention, San Francisco said Friday that it would begin to “accommodate special requests” from those who have taken the Johnson & Johnson single dose vaccine to receive “a single supplemental dose with an mRNA vaccine” such as those developed by Modern or Pfizer-BioNTech. But they must consult first with a health-care provider.

“This is an accommodation that is expected to be of interest to a small minority of J & J vaccines,” the San Francisco Department of Public Health said in a statement. The position aligns with CDC guidance that “the need for and timing of COVID-19 booster doses have not been established and are not recommended at this time,” the department said.

Fauci, speaking on NBC on Sunday, said he was hopeful that the FDA would grant full approval to the Pfizer-BioNTech vaccine by the end of August. The FDA has so far granted only emergency-use authorization for the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines.

In a separate development, Rick Bright, a vaccine expert who was disparaged by former president Donald Trump and forced out of a senior, pandemic-fighting role at the Department of Health and Human Services, has reached a settlement with the federal government over a whistleblower complaint.

The U.S. Office of Special Counsel and Bright’s attorney both announced the settlement Monday, 16 months after he was removed as director of the HHS’s Biomedical Advanced Research and Development Authority, the agency that worked early in the pandemic on coronavirus vaccine. He was reassigned to a nonsupervisory position at the National Institutes of Health.

In his whistleblower complaint, Bright contended that he was dismissed because he had disagreed with Trump over the then-president’s enthusiasm for hydroxychloroquine, an anti-malaria drug, as a coronavirus treatment.

Bright’s lawyer, Debra Katz, said the settlement included back pay and benefits from the time of his dismissal until he assumed a position in March with the Rockefeller Foundation, working with global public health organizations to prevent future pandemics. He also received compensatory damages for emotional damage from having been disparaged by Trump, who tweeted that Bright was a “creep,” and the expense of hiring security after his vilification, Katz said.

According to Katz, the special counsel is continuing to investigate a second complaint lodged by Bright, alleging that federal officials engaged in reckless behavior and steered work involving the pandemic to inappropriate contractors.

Laurie McGinley and Laura Meckler contributed to this report.