The team from Oxford University and British-Swedish biotech firm AstraZeneca began injecting doses of vaccine Vaxzevria into patients in April 2020. It’s approved for use in almost 100 countries and forms the backbone of the World Health Organization’s COVAX initiative, which aims to provide equitable access to vaccines across the globe. However, as CNET reports, the vaccine has suffered setbacks. Miscommunications with the U.S. Food and Drug Administration and dosing mistakes in clinical trials eroded confidence in the shot, then came reports in February and March showing AstraZeneca’s vaccine may be associated with a rare, sometimes fatal blood-clotting condition. Scientists aren’t sure what causes the clots with Vaxzevria or potential clotting issues with the Johnson & Johnson vaccine, which uses the same technology, and are now in a new race: unravel how Vaxzevria disturbs blood flow and learn how to manage it.