Dec 13 (Reuters) - U.S. banks have been more proactive than other industries in encouraging employees back to the office, but those plans have come under renewed scrutiny due to the rapid spread of the Omicron variant, with Jefferies Financial Group last week reversing course due to a COVID-19 outbreak among employees. Most major U.S. banks have had staff working in offices since the summer, but some are now choosing not to host holiday parties and others strongly recommending staff get booster shots. The following are the pandemic-related rules among Wall Street"s biggest banks. Bank of America Corp (BAC.N) The bank since late summer has been encouraging employees to get fully vaccinated and now to get their booster shots when eligible and offers onsite clinics in several locations. Citigroup Inc (C.N) The bank is requiring employees in the United States to be vaccinated but is not mandating boosters. It is providing rapid test kits and encouraging testing for employees going into the office, a source told Reuters. read more Deutsche Bank (DBKGn.DE) The German lender has made COVID-19 boosters available to staff at its new midtown headquarters in New York City since early November, according to a source familiar with the matter. read more Goldman Sachs Group Inc (GS.N) As infections flared up in August due to the spreading of the Delta variant, the Wall Street bank mandated vaccines for all staff and visitors entering its offices in the United States Staff in the United States must be tested onsite on a weekly basis. read more The bank is also providing access to boosters for those who are eligible, although boosters are not mandatory. Jefferies (JEF.N) The investment bank requires all staff who want to enter its offices to be vaccinated against COVID-19 and has said it will require boosters by Jan. 31, unless the person concerned is not yet eligible for the additional shot. The bank does not perform onsite testing. Last week, following a spate of cases, the bank asked staff to work from home where possible and canceled all but essential travel. JPMorgan Chase & Co (JPM.N) The biggest U.S. bank, and one of the most aggressive in bringing employees back to the office, mandated face covering for its U.S. employees in August, saying they would be required to wear masks in public indoor settings and in common areas regardless of their vaccination status. read more In October, the bank said it would restrict business travel for employees who are unvaccinated or have not disclosed their vaccination status. Such employees are required to get tested twice a week and contribute more of their pay toward medical insurance. The bank also mandated vaccines for new recruits in client-facing roles or those required to travel for business. read more Morgan Stanley (MS.N) Morgan Stanley is asking employees, contractors and visitors to show proof of vaccination before entering its New York headquarters. The bank does not require additional COVID-19 testing for staff or visitors, a spokeswoman said. Wells Fargo & Co The lender has said it strongly encourages employees to consider getting the COVID-19 vaccine, but does not require it. The bank was providing all employees with four hours of paid leave to get the booster shot if eligible. read more The bank also required employees to either document that they are fully vaccinated or get tested regularly. Fidelity Investments The company said it has paused voluntary return to office plans in New England, citing a rising risk from the COVID-19 pandemic. read more Source: Company statements, memo, sources