On Thursday, Boston biopharma company Moderna announced that its vaccine candidate, mRNA-1273, had been cleared by the FDA to move into a Phase II trial. The study, which will begin enrolling 600 participants in the coming weeks, is designed to begin assessing whether or not the potential vaccine can induce a person’s immune system to produce antibodies that recognize SARS-CoV-2.

With the news, Moderna pulls neck and neck with the current coronavirus vaccine leader: Oxford University’s Jenner Institute. Scientists there had a head start, as The New York Times reported last month. Having already acquired safety data from human trials of similar vaccines for the related coronavirus that causes MERS, Oxford researchers convinced British regulators to push forward with a large Phase II study involving 6,000 people while the outbreak in the UK is still raging. The vaccine is based on a technology that involves genetically modifying a harmless virus to create a SARS-CoV-2 look-alike that doesn’t cause disease but does trigger an immune response.

Moderna’s vaccine candidate, which was developed in collaboration with scientists at the National Institutes of Allergy and Infectious Disease, is made out of messenger RNA, hence the phrase mRNA in the vaccine’s name. This molecule is responsible for carrying the genetic recipes for making different proteins to a cell’s protein production factories. The version inside Moderna’s vaccine carries the instructions for making a little bit of the spike protein that SARS-CoV-2 uses to infect human tissues. The idea is that a vaccine recipient’s cells will produce this partial spike protein, which will train their bodies’ immune systems to recognize the virus and attack it the next time it shows up.