Schools across the United States over the weekend announced last-minute closures because of the spread of COVID-19. Students in a number of districts were slated to return to class on Jan. 3 from winter break. Some districts blamed the closures on staffing issues or the rise in cases driven by the Omicron variant. In Massachusetts, more than a dozen school districts were closed or had a delayed opening on Jan. 3, with some officials citing the spread of COVID-19 and others because of snowfall. Meanwhile, the Pittsburgh Public Schools announced that the district is shuttering 12 schools due to staffing shortages caused by COVID-19, WXPI reported. An infectious disease expert who was interviewed by the local station said that it’s “inevitable that we’re going to see cases in the school,” but stipulated that closures “can’t be tolerated.” “We have rapid tests, we’ve got antivirals, we have vaccines, we have monoclonal antibodies, and …