Meta, the parent company of Facebook, is delaying its return to US offices until March 28 and will require proof of Covid-19 booster shots for workers in those offices. The company already requires that in-office workers be vaccinated. Janelle Gale, VP of Meta’s human resources department, told CNN Business in a statement that the move is intended to give employees “more time to choose what works best for them.” “We’re focused on making sure our employees continue to have choices about where they work given the current COVID-19 landscape,” Gale said. “We understand that the continued uncertainty makes this a difficult time to make decisions about where to work.” Meta employees must now decide by March 14 how they would like to continue working — whether in the office, full-time remote, or temporarily from home for another 3-5 months. With the decision, Meta becomes one of the first major US corporations to require proof of a booster shot from its in-office employees, not just vaccination, amid the rapid spread of the Omicron variant. It joins a growing list of state governments, colleges and universities, and other employers across the country that now say a booster is necessary for in-person work. The trend could soon continue more widely as health officials debate changing the definition of “fully vaccinated” to mean three doses of the Covid-19 vaccine, up from two. Last month, the market research firm Gartner predicted that by mid-January, as many as 15% to 20% of companies it surveys could have booster requirements for its workers.