Facebook threw its weight behind promoting Covid-19 vaccines—“a top company priority,” one memo said, Activists flooded the network with what Facebook calls “barrier to vaccination” content, the internal memos show. They used Facebook’s own tools to sow doubt about the severity of the pandemic’s threat and the safety of authorities’ main weapon to combat it. The Covid-19 problems make it uncomfortably clear: Even when he set a goal, the chief executive couldn’t steer the platform as he wanted. A Facebook spokesman said in a statement that the data shows vaccine hesitancy for people in the U.S. on Facebook has declined by about 50% since January