Vaccine and mask requirements: Big employers react to the Delta variant.

With the coronavirus spreading across the country and hospitalizations rising again, and public health officials warning that the Delta variant carries new risks even for vaccinated people, big businesses are rethinking their plans.

Some are delaying their plans to bring workers back to the office, and others are restoring mask requirements for customers. In the last week, several have also imposed vaccine mandates, after having held off on such a step for months.

The decision to require vaccines was endorsed on Sunday by the director of the National Institutes of Health. Speaking on CNN’s “State of the Union,” Dr. Francis Collins said that asking employees for proof of vaccination or regular testing were steps “in the right direction.”

Here’s how some big businesses changed their plans in late July:

Delayed return to office:

• Lyft pushed back its return-to-office date to February from September, Google extended its work-from-home policy to mid-October, and Apple said employees would not be expected to return to the office until at least Oct. 1, a month later than before.

• Uber said that it would not require employees to return until Oct. 25, instead of its initial September date, and that a further delay was possible if cases kept rising.

• Twitter shut its San Francisco and New York offices, putting a halt to reopening plans without a timeline in place.

• The New York Times Company also indefinitely postponed its planned return to the office, telling employees that they would be given four weeks notice before being expected to return. The company, which employs about 4,700 people, had planned for workers to start to return for at least three days a week in September. Its offices will remain open for those who want to go in voluntarily, with proof of vaccination.

• Endeavor, the parent company of the William Morris Endeavor talent agency, closed its recently reopened offices after Los Angeles County reimposed its indoor mask mandate. An Endeavor spokesman said the company had decided that enforcement would be too difficult and would hinder group meetings.

Vaccine requirements:

• Walmart, the nation’s largest private employer, with nearly 1.6 million workers, said vaccines would be mandatory for employees in its headquarters and for managers who traveled in the United States. The mandate does not apply to much of its work force — employees in stores, clubs, and distribution and fulfillment centers.

• The Walt Disney Company said salaried and nonunion hourly U.S. employees at its sites must be fully vaccinated. Unvaccinated workers who are already on site will have 60 days to get the immunization, and new hires will be required to be fully vaccinated before starting work.

• The Washington Post will require all employees to show that they are vaccinated against the coronavirus as a condition of employment, starting when workers return to the office in September.

• Netflix said it would require the casts of all its U.S. productions to be vaccinated, along with anyone else who comes on set.

• Facebook said it would require employees who work at its U.S. campuses to be vaccinated, depending on local conditions and regulations.

Masks requirements:

• Walmart said it was reinstating mask requirements for associates in areas of the country with substantial or high transmission rates. The company recommended that customers wear masks in those areas, too. The retailer also doubled its reward to employees who get vaccinated from $75 to $150.

• Starting Monday, the Florida-based grocery chain Publix will require employees to wear masks in all its stores regardless of their vaccination status.

• Apple said employees and customers would have to wear masks regardless of their vaccination status in more than half its stores in the United States. Apple said the stores would be determined by the rate of coronavirus cases in the area. Apple also told its employees that they would have to wear masks when inside the company’s main offices in the United States, regardless of whether they were vaccinated.