Companies are monitoring the spread of the delta Covid variant as they adapt return-to-office plans and prioritize giving flexibility to employees, a board member at three Fortune 500 companies told CNBC on Friday.

“I believe there’s going to continue to be hybrid offerings. … Flexibility is here to stay, especially if you want to be competitive for talent,” said Shellye Archambeau, a director at Verizon, Nordstrom and Roper Technologies. She’s also a former CEO of MetricStream, which makes governance, risk management and compliance software.

Archambeau said that business’ reopening concerns are being driven by the highly transmissible delta variant, first discovered in India. It’s now the dominant strain of Covid in the United States and causing cases and deaths to increase again, particularly across largely unvaccinated communities.

“Companies are watching the data very carefully,” Archambeau said. “What I’m seeing is they’re trying to remain flexible, creating the optionality for employees to come back to work but still watching the numbers and how the rates are going.”

Archambeau’s remarks come as major companies try to figure out how to safely return to the office.

• Apple postponed its return-to-work plans by at least a month to October, rolling back its initial proposal to bring employees in three days a week starting in September. 
• Facebook, Slack and Square are sticking to a mostly remote workforce.
• Companies like Alphabet‘s Google, Amazon and Microsoft are implementing plans that allow employees to split their time between home and the office.
• Twitter and Spotify have boasted permanent work-from-home policies.

Few companies are mandating employees to be fully vaccinated before returning to the office, Archambeau said. Instead, she said companies are strongly encouraging and trying to make it easier for employees to get vaccinated, even making it voluntary to return to the office and encouraging mask-wearing and physical distancing protocols for unvaccinated workers.

According to a survey conducted in April by Arizona State University with support from the Rockefeller Foundation, more than 60% of companies in the U.S. will require proof of vaccination from their employees while 44% will require all employees to get vaccinated and 31% will encourage vaccinations.

Archambeau, a strategic advisor to the president of ASU, said that peer pressure will soon begin to play a bigger role in pushing employees to get vaccinated.

More employees may also return to the office when children get vaccinated, allowing them to continually go to school, participate in in-person activities and rely on child-care services.

“I think as time goes through, companies are absolutely strongly encouraging employees to be vaccinated,” Archambeau said. “The way in which they’ll be able to work, the kinds of roles they’ll be able to play, I think, in time will be affected by whether they’re vaccinated or not. … People will want to be vaccinated in order to actually do well within the company.”