The United States is averaging about half a million new coronavirus vaccinations per day for the first time since June, officials with the White House covid-19 response team said Thursday.

During an afternoon news briefing, the team praised the nation’s vaccination progress. Task force head Jeffrey Zients noted that the average number of 12-to-17-year-olds getting the shots has doubled in the past month as students return to classrooms.

States with the highest virus case rates have made the greatest strides in increasing immunizations, he said. The average number of shots given per day has nearly tripled in Arkansas and quadrupled in Louisiana, Alabama and Mississippi in the past month.

“We’re getting more shots in arms in the places that need them the most,” Zients said. “That’s what it’s going to take to end this pandemic: more vaccinations, more Americans doing their part and rolling up their sleeve.”

The vaccination news comes as the nation continues to experience an increase in coronavirus cases, hospitalizations and deaths. Ninety percent of U.S. counties are now experiencing substantial or high transmission of the virus, Centers for Disease Control and Prevention Director Rochelle Walensky said.

“Those at highest risk remain people who have not yet been vaccinated,” she noted.

Here are some significant developments:

  • A surge in coronavirus patients and a shortage of health-care workers and intensive care unit beds have pushed Mississippi’s hospital system to the brink of “failure,” state health officials warned Wednesday, saying drastic federal intervention was needed.
  • The spread of the delta variant is igniting covid hot spots in highly-vaccinated parts of the United States.
  • Americans are sneaking extra coronavirus shots as officials are weighing who should receive them.
  • Hospitals in coronavirus hot spots across the U.S. are struggling with staff shortages. The problem is particularly acute in the South, where the delta variant and low vaccination rates are driving record hospitalizations.
  • Virginia Gov. Ralph Northam (D) is mandating masks inside all K-12 schools, even for the vaccinated.

The White House covid-19 response team confirmed that the Food and Drug Administration plans to authorize extra doses of coronavirus vaccines for patients with weakened immune systems.

This action is about ensuring our most vulnerable, who may need an additional dose to enhance their biological responses to the vaccines, are better protected against covid-19,” Walensky said, adding that it was especially important as the delta variant spreads.

The move, expected as soon as Thursday, could mean additional shots will be available for that vulnerable population as soon as this weekend.

The FDA action on the immunocompromised is likely to affect transplant patients who take immune-suppressing drugs to prevent rejection of new organs and others who have diseases, including blood cancers, that damage the immune system. They are more likely to become seriously ill from covid-19, experts say.

Making such patients eligible for an extra shot, doctors say, is preferable to having worried patients seek out additional inoculations illicitly — which is already happening.

The timing of the expected action was described by people with knowledge of the process who spoke on the condition of anonymity because they were not authorized to speak publicly. The Washington Post first reported Friday that action on the shots was imminent.

The nation’s top infectious-disease expert, Anthony S. Fauci, said Thursday on ABC’s “Good Morning America” that the decision to administer booster shots would apply to “a relatively small proportion of the population, around 3 percent or so,” and in particular transplant patients and those undergoing therapies for cancer.

As for the wider population, Fauci told CBS on Thursday: “We don’t feel at this particular point that apart from the immune-compromised … we need to give boosters right now.”

Fauci said that decisions were still being made about booster shots for the wider population. “No vaccine is going to last forever,” he said on ABC. “We’re going to be ready and have a plan.”

The next step in the process for immune-deficient patients occurs Friday, when a CDC advisory committee is scheduled to vote on recommending whether people should get the extra doses. The panel is expected to endorse the idea and urge patients to talk to their doctors about it. Walensky is expected to sign off on the decision Friday afternoon.

The FDA said it is “closely monitoring data as it becomes available from studies administering an additional dose of the authorized covid-19 vaccines to immunocompromised individuals. The agency, along with the CDC, is evaluating potential options on this issue, and will share information in the near future.”

Booster shots have begun in a handful of other countries, including Israel, where people over 60 who have received their second shot at least five months earlier are eligible for a booster, as are the immunocompromised. France, Germany and Britain are planning to give booster shots starting in September. The World Health Organization has called for a moratorium on additional doses until at least September — with billions of people globally yet to receive their first shot.

On Wednesday, Chile began administering booster shots to those inoculated with Sinovac’s coronavirus vaccine. Almost 70 percent of its population has been fully vaccinated, predominantly with China’s Sinovac shot, but authorities last week said studies have shown that a booster was necessary to shore up immunity. Lines of elderly citizens, eager to participate in the campaign, formed at vaccination centers across the capital, Santiago, Reuters reported.

“They arrived very early, like on an election day, very well dressed, very happy,” Rodolfo Carter, mayor of La Florida on the outskirts of the city, told the outlet. “I think it is a great sign of hope.”

California Gov. Gavin Newsom (D) on Aug. 11 mandated that teachers and school staff "submit a verification of vaccination and/or submit to weekly testing." (Reuters)

As the delta variant continued fueling a surge in cases across the United States, more authorities announced measures aimed at slowing the spread.

Virginia will require all students, teachers and staff in K-12 schools to wear masks indoors this fall, regardless of vaccination status, Gov. Ralph Northam (D) announced Thursday.

San Francisco will require proof of vaccination for entry to some indoor businesses, including bars, restaurants, clubs, theaters and fitness establishments, Mayor London Breed (D) and Director of Health Grant Colfax said.

The Department of Veterans Affairs announced expanded vaccine mandates for 245,000 employees in its sprawling health-care system. The new requirement comes two weeks after Secretary Denis McDonough announced 115,000 front-line health-care workers had eight weeks to be inoculated, making VA the first agency in the federal government to enact a mandate.

The directive applies to most staff, volunteers and contractors at the Veterans Health Administration who come into contact with patients and health-care workers, including psychologists, pharmacists, social workers, nursing assistants, physical therapists, respiratory therapists, peer specialists, medical support assistants, engineers, housekeepers and others.

“This pandemic is not over and VA must do everything in our power to protect Veterans from COVID-19,” McDonough said in a statement. The mandate will apply to a total of 360,000 agency employees, the vast majority.

Also Thursday, the National Education Association threw its support behind policies that require teachers to get vaccinated or submit to regular testing, weighing in on the heated debate over how far schools should go to stop outbreaks within their walls.

The president of the association, the nation’s largest labor union with nearly 3 million members, said the requirements were needed to help ensure students could return to classrooms uninterrupted by closures or quarantines.

“NEA has said from the beginning that we need to follow the science, and evidence shows that COVID-19 vaccines, combined with other safety measures, are the most powerful weapon we have against the pandemic,” said Becky Pringle, who added that 90 percent of the association’s members reported getting vaccinated. “We believe that such vaccine requirements and accommodations are an appropriate, responsible, and necessary step to ensure the safety of our school communities and to protect our students.”

More large companies announced their offices will remain closed for longer than expected. Facebook is delaying its return to office for U.S. employees until January 2022, the company said Thursday. Facebook had planned to bring back 50 percent of its employees in September, and the rest in October. Amazon also said last week it would push back its mandatory return date for office workers to January. Facebook is requiring employees who work onsite to be vaccinated, the company said last month.

Moriah Balingit, Rachel Lerman and Lisa Rein contributed to this report.