July 29 (Reuters) - Uber Technologies Inc (UBER.N) is pushing back its back-to-office date to late October globally, and all employees in the United States will have to be fully vaccinated before returning to office, a spokesperson said on Thursday. The news comes a day after major tech companies including Twitter Inc (TWTR.N), Alphabet Inc"s (GOOGL.O) Google and Facebook Inc (FB.O) said all U.S. employees must get vaccinated to step into offices, as the highly infectious Delta COVID-19 variant drives a resurgence in cases. In April, Uber said it expected its employees to return to office by Sept. 13. San Francisco-based ride-hailing company Lyft Inc (LYFT.O) has also postponed its reopening to February from September. The Delta variant, which emerged in India, has quickly spread globally and now accounts for more than 80% of all U.S. coronavirus cases. Uber"s news was first reported by Business Insider earlier on Thursday.