All adults in America are now eligible for a covid-19 vaccine. Around 30% of those polled in the country, however, are hesitant to take the jab. A shortage of vaccines will soon become a shortage of arms. What is the best way to persuade reluctant citizens to get inoculated?   We speak to Heidi Larson, anthropologist at the London School of Hygiene and Tropical Medicine and founding director of the Vaccine Confidence Project, about the similarities between vaccine hesitancy today and the 19th century. Crystal Son, director of healthcare analytics at Civis Analytics, on why vaccine safety messaging is ineffective.   Alok Jha and Natasha Loder are joined by Edward Carr, The Economist’s deputy editor, and Tamara Gilkes Borr, US policy correspondent.   For full access to The Economist’s print, digital and audio editions subscribe at economist.com/thejabpod. Sign up for our new weekly science and data newsletters at economist.com/simplyscience and economist.com/offthecharts   See acast.com/privacy for privacy and opt-out information.