Now that the vaccine rollout is reaching a critical stage in which most adults who want the vaccine have gotten it, but many others are holding out, these 12 influential social media users stand to have an outsize impact on the outcome. These figures are well-known to both researchers and the social networks. Some of them run multiple accounts across the different platforms. They often promote "natural health." Some even sell supplements and books. Many of the messages about the COVID-19 vaccines being widely spread online mirror what's been said in the past about other vaccines by peddlers of health misinformation. "It's almost like conspiracy theory Mad Libs. They just inserted the new claims," said John Gregory, deputy health editor at NewsGuard, which rates the credibility of news sites and has done its own tracking of COVID-19 and vaccine misinformation "superspreaders."