JPMorgan Chase & Co. instructed unvaccinated staff in Manhattan to work from home from Tuesday, a further sign that banks and other financial firms are tightening protocols as COVID-19 infections rise and the Omicron variant spreads.

The U.S. bank, one of the most aggressive in bringing employees back to the office, had previously allowed unvaccinated staff to work in its Manhattan offices provided they were tested twice a week.

In a memo to staff on Monday, the bank urged unvaccinated staff to get vaccinated and for those who are eligible to get booster shots. It also relaxed mask requirements for vaccinated staff working in its Manhattan offices.

"We continue to agree with health authorities that being vaccinated against COVID-19 is the best way to keep ourselves and our loved ones safe - especially as we face the winter months and a new variant - so please consider getting vaccinated if you aren't already, and getting your booster if you are," the memo said.

U.S. financial firms have been more proactive than other industries in encouraging employees to return to offices. But the recent surge in cases has caused some to rethink their strategies.

New York State's Department of Health had issued a mask mandate effective Monday requiring any individual entering an office that does not require vaccination to wear a mask at all times.

"It seems unfair to require our vaccinated employees to wear masks all day at their desks, and would be a step that would slow the progress we've already made toward business normalcy," JPMorgan said in the memo.

More than 90% of JPMorgan staff based in Manhattan are vaccinated, according to the memo.

Vaccinated staff will now have to wear face coverings only when walking through lobbies, riding in elevators and in cafes when not eating.

The bank added that the memo does not apply to branch staff, who "will continue to follow their established procedures and protocols."

Other banks and financial firms have been taking steps to protect staff as infection and hospitalization rates increase in New York and other states.

Last week, investment bank Jefferies Financial Group asked staff  to work from home again due to a spate of COVID-19 cases.

Asset management firm Fidelity Investments on Monday said it had paused some voluntary return-to-office plans.