Visitors to the National Academy of Sciences (NAS) in Washington, D.C. ... must show a guard proof that they have been vaccinated against COVID-19. Such demands were common around the world a year ago. But by now, almost everyone has had natural infections with SARS-CoV-2 or been vaccinated against the coronavirussometimes both"and it's become clear that vaccine-induced immunity quickly loses its ability to prevent infection and spread of the latest variants. Some now say the mandates are outdated. The persistent requirements are "baffling to say the least," says Heidi Larson, an anthropologist at the London School of Hygiene & Tropical Medicine and director of the Vaccine Confidence Project. She spoke at a major infectious disease meeting this year that required all attendees to show they had had two doses of a vaccine"with no need for a recent booster. "It's not like it's going to mitigate the spread." Larson and other vaccine acceptance researchers who spoke to Science all emphasize that COVID-19 vaccines clearly prevent severe disease, but they worry maintaining the mandates could undermine future public health efforts. "Having to show these old vaccination proofs or certificates really doesn't make sense, and it could cause harm, because people might lose trust in the competence of the organization," says University of Konstanz psychologist Katrin Schmelz. Compared with Europe and Asia, the United States appears to be holding on to vaccine mandates more tightly.