The exchange joins investment banks such as Goldman Sachs, JPMorgan Chase & Co and Morgan Stanley, which also said on Friday that they were dropping the requirement for staff to wear masks in the office.

Goldman Sachs will no longer require masks to be worn by employees at its U.S. offices from Monday and will leave it to individuals to decide if they want to mask up, a spokeswoman at the bank said.

For fully vaccinated employees of JPMorgan working out of their U.S. offices, masks have been made completely voluntary, according to a memo seen by Reuters.

A large percentage of JPMorgan's staff has been vaccinated, the memo sent to all U.S. employees said, adding that contact tracing and mandatory bi-weekly testing will be carried out for unvaccinated staff entering the offices.

Staff at Morgan Stanley's offices will not be required to wear masks, a spokeswoman for the bank said, as only vaccinated employees are allowed into their buildings.

Major U.S. banks have rolled out plans to bring their staff back to office in recent weeks after the number of COVID-19 cases registered a drop.

(Reporting by Matt Scuffham and David Henry in New York, Anirudh Saligrama and Sohini Podder in Bengaluru; Editing by Krishna Chandra Eluri and Sandra Maler)