A COVID-19 outbreak unfolded at a conference held by the U.S. Centers for Disease Control and Prevention (CDC) despite most attendees being vaccinated. About 1,800 CDC staffers and others gathered in April in a hotel in Atlanta, where the CDC is headquartered, for a conference focused on epidemiological investigations and strategies. On April 27, the last day of the conference, several people notified organizers that they had tested positive for COVID-19. The CDC and the Georgia Department of Public Health worked together to survey attendees to try to figure out how many people had tested positive. “The goals were to...