Results from 6-year-old Anastasia Weaver’s autopsy may take weeks. But online anti-vaccine activists needed only hours after her funeral this week to baselessly blame the COVID-19 vaccine. A prolific Twitter account posted Anastasia’s name and smiling dance portrait in a tweet with a syringe emoji. A Facebook user messaged her mother, Jessica Day-Weaver, to call her a “murderer” for having her child vaccinated. In reality, the Ohio kindergartner had experienced lifelong health problems since her premature birth, including epilepsy, asthma and frequent hospitalizations with respiratory viruses. “The doctors haven’t given us any information other than it was due to all...