Small-business owners are confronting challenges preparing for the Biden administration’s vaccine mandate, with some saying efforts to comply are exacerbating hiring problems and stoking tensions with and among workers.

Under new federal rules, employers with 100 or more workers must ensure employees get fully vaccinated or else test negative for Covid-19 at least weekly and wear a mask at work. A federal appeals court temporarily blocked implementation of the rules in response to legal challenges, and the Occupational Safety and Health Administration agreed not to begin enforcement pending a court decision. Many business owners are nonetheless preparing for the mandate, slated to take full effect Jan. 4.