BlackRock Inc. and Wells Fargo & Co. are pushing their return-to-office plans back a month to early October, citing rising Covid-19 rates across the U.S.

BlackRock is allowing workers to choose whether or not to come into U.S. offices through Oct. 1, according to a memo. Wells Fargo, with almost 260,000 employees, will now begin bringing back staffers who have been working remotely starting Oct. 4 rather than Sept. 7, as previously announced, according to an internal memo Thursday from Chief Operating Officer Scott Powell.

The shift from both the world’s largest money manager and the firm with the largest workforce of any U.S. bank signals the financial industry is rethinking its return-to-office plans as the highly contagious delta variant sweeps across the country. While the biggest U.S. banks have so far stopped short of requiring their employees to be vaccinated, BlackRock has only allowed fully inoculated workers to come back, joining technology giants such as Alphabet Inc.’s Google and Facebook Inc.

The delta variant “raises concerns about returning to the office – even for those who are vaccinated and particularly for those of you with dependents at home who are currently ineligible for the vaccine,” according to the BlackRock memo, which was signed by executives including Chief Operating Officer Rob Goldstein.

San Francisco-based Wells Fargo has resumed a requirement that all employees currently working in offices wear masks, regardless of their vaccination status, according to a spokesperson.

At BlackRock, staff will have the choice whether or not to put on a mask, except where it’s mandated by local laws, like Atlanta, San Francisco, Santa Monica and Washington. Since July, the company has been in a “re-acclimation” period, during which it’s asking vaccinated employees to begin adjusting back to office work if they feel comfortable with it.

California and New York City, where BlackRock is based, have said government employees will need to be vaccinated or submit to weekly tests.

“The delta variant does not change the basic facts: vaccinated people are at lower risk of becoming infected with Covid-19, and much lower risk of becoming seriously ill and requiring hospitalization if they do become infected,” Powell wrote in the Wells Fargo memo. The bank is offering eight hours paid time off for employees to get vaccinated. “Please take advantage of the extra time off that Wells Fargo offers for you to get vaccinated.”

This article was provided by Bloomberg News.