President Biden is urging state and local governments to give $100 to anyone newly vaccinated against the coronavirus, part of a push to boost immunizations as infections and hospitalizations rise with the swift spread of the delta variant of the virus.

Cities and states have already turned to multimillion-dollar lotteries, free food and other incentives to sway the millions of Americans who remain hesitant about or outright opposed to highly effective vaccines. With the country now facing what the Biden administration calls a “pandemic of the unvaccinated” — and the highly contagious delta variant spurring some renewed restrictions — governments are under new pressure to get shots into the arms of the reluctant.

A slew of announcements Thursday signaled Biden’s more aggressive approach, as he said all federal employees must get immunized or face new testing, masking and distancing rules — a shift that will affect more than 4 million people. Biden is also asking the Defense Department to “look into how and when” it will require vaccinations for members of the military, the White House said.

The federal push for cash incentives follows New York City’s announcement of $100 giveaways this week. Minnesota Gov. Tim Walz (D) quickly said after Biden’s announcement Thursday that his state would follow suit.

The Treasury Department emphasized in a Thursday news release that funding for vaccine incentive programs can come from the $350 billion in pandemic relief given to state, territorial and local governments in a $1.9 trillion stimulus package passed in March.

“For these governments and the communities they represent, no task is more urgent than turning the tide on the pandemic, and there is no better tool than vaccination,” the Treasury Department said. While some have questioned the effectiveness of cash rewards, the White House covid-19 response team said in a tweet that “we’ve seen financial incentives work in the past.”

Here are some significant developments:

  • The delta variant appears to cause more severe illness than earlier variants and spreads as easily as chickenpox, according to an internal federal health document that argues officials must “acknowledge the war has changed.”
  • Sacramento County and D.C. on Thursday joined a growing list of major metropolitan areas ordering all residents to wear masks indoors, regardless of vaccination status.
  • The four-day Lollapalooza music festival is underway in Chicago, raising fears about the virus spreading in the throngs of attendees. With 100,000 concertgoers expected each day, the event ranks as one of the biggest public gatherings the United States has seen since the pandemic began.
  • The pharmaceutical giant Pfizer predicted Wednesday that coronavirus vaccine boosters would soon be needed, a declaration that came on the same day the company published data showing that its shots remained robustly protective six months after vaccination.
  • Israel is now moving toward making booster shots available for older adults, after Health Ministry experts agreed late Wednesday that a third dose of the Pfizer-BioNTech vaccine should be offered to the elderly. The experts cited local data showing an apparent decline in the vaccine’s efficacy over time, as well as a surge in new cases fueled by the delta variant.

A University of California at Los Angeles study found that about one-third of unvaccinated people said that cash incentives would make them more likely to get immunized.

The move comes after federal health officials this week called for people to resume indoor masking in virus hot spots. Sacramento County and D.C. on Thursday joined a growing list of major metropolitan areas ordering all residents to mask up indoors, regardless of vaccination status. The delta variant is causing infections to spike in all 50 states, some of which are now reporting daily case numbers not seen since the worst months of the pandemic.

Sacramento County’s masking order applies to all residents in all public indoor settings. The region has seen its daily case rate more than triple over the past month, from about 5 per 100,000 at the end of June to 18.3 per 100,000 on July 20, according to the health department. Less than half of the population is vaccinated in the county of 1.5 million.

D.C., too, is facing an alarming spike in infections. The case rate has risen by nearly 44 percent over the past week, though it remains far lower than it was during the worst months of the pandemic, according to Washington Post data.

The District previously had one of the country’s strictest mask mandates, requiring residents to use face coverings both indoors and outdoors when people came in close contact for more than a “fleeting” amount of time. Officials lifted the mandate for all residents in June.

Similar mandates are reemerging around the country. Nevada officials brought back the state’s indoor mask mandate following this week’s announcement by the Centers for Disease Control and Prevention that everyone should start masking up indoors again in places where viral transmission is high.

Officials have also revived mandates in Los Angeles County; St. Louis; Kansas City, Mo.; and Savannah, Ga. Other cities and states, including California, said they recommended indoor masking but stopped short of requiring face coverings.

On Wednesday, the Defense Department said it was requiring everyone, regardless of vaccination status, to wear masks indoors at military facilities in areas where transmission is high. The rules mirror the new guidance from the CDC, covering all service members, federal employees, on-site contractor employees and visitors.

In Florida, Walt Disney World Resort announced Wednesday that it’s now requiring all guests to wear masks indoors, reversing a June decision not to mandate them for the vaccinated. The rules take effect from Friday for all guests ages 2 and up.

“As we have done since reopening, we’ve been very intentional and gradual in our approach to our covid-19 health and safety protocols,” Disney said in a statement. The company added, “We encourage people to get vaccinated.”

With cases rising, some employers are taking the additional step of mandating vaccinations at their businesses. In New York, restaurant mogul Danny Meyer announced Thursday that his eateries would require vaccines for all staff members and that diners show proof they’ve gotten the shots.

The rise of the delta variant has complicated the return of large gatherings. In Chicago, the massive Lollapalooza music festival kicked off Thursday, drawing tens of thousands of revelers to the city’s downtown and renewing worries about the coronavirus spreading in the tightly packed crowds.

The four-day festival is expected to be one of the largest gatherings in the United States since the pandemic began. About 100,000 people are set to attend each day of the event, which is being held at Chicago’s Grant Park and will feature 170 bands on eight stages.

Organizers say those attending will need to show proof of full vaccination or a negative coronavirus test if unvaccinated. The unvaccinated must also wear a mask throughout the site.

Even well-ventilated, outdoor sites pose risks, according to infectious-disease experts. Festivalgoers are likely to have a hard time keeping the necessary physical distance when crowds are packed in, and everyone is dancing, singing, sweating, and drinking.

There is also a risk of increased transmission at chokepoints such as entrances, bathroom lines and at the space nearest to the stage where crowds tend to pack in the tightest, experts say.

On Thursday at Lollapalooza, Andrea Garcia of Nashville was among the few masked in a throng of people pouring toward the stage where rockers Jimmy Eat World were about to play. Garcia, who said she has been fully vaccinated, opted to wear a surgical mask at the festival after checking the coronavirus infection rate in Chicago.

The festival’s vaccination or negative test policy for entry provided Garcia some reassurance. But seeing the festival lengthen the window for a negative test result to 72 hours “frightened me a bit,” Garcia said.

“I’m still skeptical, but am trying to make the best of it,” she said. “We try to be safe.”

As the Olympics entered their second week in Tokyo, the Japanese government on Thursday announced it was planning to extend a state of emergency in the city and expand the measure to four other regions as the nationwide number of new daily coronavirus cases soared past 10,000 for the first time, local media reported.

The rapidly growing outbreak has cast a shadow over the Games, where authorities reported a record number of new infections for the third straight day Thursday.

Olympic athletes and other visitors are under strict rules separating the Games from the rest of the city. But organizers Thursday announced another 24 infections among competitors and attendees, including two who were hospitalized.

The new cases brought the total number of Games-related infections to 193 since July 1. The state of emergency in Tokyo and other regions such as Okinawa will last until Aug. 31, according to media reports.

Experts in Japan warned of a deepening crisis they said could quickly overwhelm the health-care system if more-stringent measures are not imposed.

“The greatest danger now is that the severity of the current situation isn’t being communicated to the public,” Japan’s top medical adviser, Shigeru Omi, told a parliamentary panel Thursday.

“If that sense of urgency isn’t conveyed sufficiently, the virus will spread further and the burden on the health-care system will become increasingly severe,” he said.

Japan has refrained from enacting hard shutdowns and instead relies on a generally cooperative public to adhere to health protocols such as masking and social distancing.

The state of emergency designation mostly generates stricter rules for restaurants and other entertainment venues, including earlier closing times. Central Tokyo, however, has remained crowded during the day, with many residents ignoring the regulations.

As a result, hospitalizations are on the rise. Authorities blame the swift-moving outbreak on the more contagious delta variant now present in at least 132 countries, according to the World Health Organization.

Julie Zauzmer contributed to this report.