ToplineTwitter has shut down its headquarters and stopped all plans to reopen it, just two weeks after it allowed staff to return to work. This is because employers across the country are struggling to restore in-person employment, while coronavirus cases rise and vaccination rates plateau.An exterior sign was posted at the Twitter headquarters in San Francisco. Getty ImagesThe Key FactsTwitter announced that it is closing its San Francisco headquarters as well as New York offices. Future office reopenings will be halted, according to a spokesperson for the company. Twitter cited Tuesday's Centers for Disease Control and Preventions guidance, which advised all Americans to wear masks indoors in areas with high levels of Covid-19 transmission. This list currently includes San Francisco and all five New York City boroughs. The closure follows 16 days of Twitter's New York and San Francisco offices being reopened after more than a decade of mandatory work-from home orders. However, the company allowed employees to still work remotely. In mid-July, Twitter's CFO Ned Segal posted the following tweet:Surprising FactForbes confirmed that Twitter required its staff to show proof of vaccination before it closed its office.Big NumberMore than 5,500. According to Twitter's annual report, that is how many Twitter employees were employed in December 2020. The spokesperson for Twitter did not provide details about the number of employees who work in the New York and San Francisco offices.Important BackgroundCoronavirus infections are on the rise in all 50 states. This is despite months of hope-inducing declines. Experts attribute this trend to the more contagious Delta virus and stubbornly low vaccination rates in some U.S. communities. Although some employers have plans to reopen their workplaces, they believe that vaccination is the best way to get employees back. Morgan Stanley, Google, and Facebook require employees to show proof of their vaccination status before they can enter the office again. MGM Resorts is joining the states of New York, California, and telling staff that they have to decide between getting vaccinated and taking compulsory Covid-19 tests. The President Joe Biden, America's largest employer, is considering a similar mandate regarding vaccines or tests for the federal government.Continue readingFacebook is the latest company to require workers to get vaccinated in the midst of the Covid Surge. (Forbes)