When news leaked this month that AstraZeneca was halting its coronavirus vaccine trial, the company explained that it was “a routine action.” The goal, to determine whether one participant’s illness was linked to the vaccine, was heralded by scientists as exactly how trials are supposed to work: putting safety first. But Children’s Health Defense, a group that has peddled misinformation and conspiracy theories about vaccines for years, reacted with alarm. It quickly posted about the news on its website and social media accounts, and its founder, Robert F. Kennedy Jr., declared without basis that pharmaceutical companies “have always been able to dismiss these sort of tragic outcomes as sad ‘coincidence.’” “Vaccines are not accustomed to this level of scrutiny,” the organization tweeted.