Citigroup Inc. told employees returning to offices in the New York area and other big U.S. cities that they’ll need to be vaccinated against Covid-19, among the more restrictive moves by a U.S. financial firm as companies contend with the deadly virus and its highly contagious delta variant.

The decision also affects workers in Chicago, Philadelphia, Boston and Washington, D.C., the bank told employees in a memo Tuesday. Citigroup expects employees to return to offices starting Sept. 13.

Staffers at the company’s bank branches are encouraged but not required to get Covid-19 vaccines. Mask-wearing is required for all office and branch workers regardless of whether they’ve gotten shots, Citigroup said.

Citigroup’s requirement follows similar moves by Morgan Stanley, which said in late June that it would bar workers who aren’t vaccinated from entering its offices in the New York area, and Jefferies Financial Group Inc., which is mandating that employees who wish to return to its offices must be fully vaccinated.

Most of Wall Street’s biggest banks have so far stopped short of requiring employees to be vaccinated. That contrasts with Silicon Valley giants such as Facebook Inc. and Alphabet Inc.’s Google, as well as the state of California and New York City, which have said government employees will need to be vaccinated or tested weekly. With the rise of Covid-19’s delta variant, which has shown its ability to jump between vaccinated people, Wall Street executives have struggled with how to calibrate their responses.

This article was provided by Bloomberg News.