WASHINGTON—With the growth in the Delta variant, the Pentagon appears poised to mandate vaccinations against COVID-19. Officials told Reuters a decision on the next steps could come within days. The U.S. military says around half the U.S. armed forces are already fully vaccinated, a number that climbs significantly when counting only active-duty troops and excluding National Guard and reserve members. Vaccination rates are highest in the Navy, which suffered from an outbreak last year aboard an aircraft carrier. About 73 percent of sailors are fully vaccinated. That compares with the U.S. national average of about 60 percent of adults ages 18 and over who have been fully vaccinated. Because U.S. troops are generally younger and fitter, relatively few U.S. servicemembers have died as a result of COVID-19—just 28 in total, according to Pentagon data. For the general U.S. population, however, the pandemic has led to the biggest decline in life …