OMAHA, Neb.—U.S. factories have been cranking out goods during much of the pandemic at rates that are remarkably close to normal. However, manufacturers are concerned they may not be able to keep pace until most of the country is vaccinated because the coronavirus continues to surge in areas where many plants are based. Safeguards that were put in place after the initial wave of the virus appear to have prevented the large outbreaks that sickened hundreds of workers and forced automakers, meat processors, and other businesses to halt production last spring. But with the nation’s COVID-19 death toll eclipsing 300,000 and the virus spiking in communities that surround the plants, industry and union officials say it may be impossible to keep the virus out of factories. “We are seeing an increase in the number of positive (test) rates like you’re seeing in the surrounding communities,” said Gary Johnson, chief manufacturing …