http://www.sciencemag.org/news/2021/01/compelled-stories-marketing-expert-s-tips-promoting-covid-19-vaccination

Research suggests giving people visible indicators that they have received a COVID-19 vaccine, such as stickers or bracelets, could help persuade others to get the shots.

Science’s COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.