Scientists have discovered a new type of antibody that helps the COVID-19 virus infect cells in people who have already been infected with the Delta variant, but not in those who have been vaccinated or infected with other variants. This antibody, called ConD-854, binds to a specific part of the virus and enhances its ability to enter cells, making it more likely to cause infection. The researchers found that this antibody works differently than previously discovered antibodies and provides new insights into how the immune system responds to COVID-19.