Jefferies will only allow employees back into its offices if they have been vaccinated against Covid-19, as executives raise concerns about an increase in infections among its staff.

Rich Handler, the firm's chief executive, and chairman Brian Friedman, told staff in a letter that the move was in reaction to employees' health and safety concerns. There have been 40 cases of Covid-19 among Jefferies' employees in the past month, according to the letter.