A pandemic may be a tough time to test a new technology, but that’s exactly what COVID-19 vaccine experts are doing, with encouraging results. Two of the first shots that could be injected into people’s arms as early as December, from Pfizer and Moderna, rely on a new technology based on a genetic material called mRNA.This method is both fast and flexible; vaccine makers don’t need to grow or manipulate the COVID- 19 virus—all they need is its genetic sequence.That efficiency led to shots that are more than 90% effective in protecting against COVID-19, which were developed and tested in record time. —Alice Park