U.S. Supreme Court Justice Amy Coney Barrett on Thursday denied a bid by students at Indiana University to block the school’s requirement that they be vaccinated against COVID-19.

       Barrett rejected the students’ emergency request without offering any explanation. The decision marks an early test of vaccine mandates amid a spike in infections and hospitalizations caused by the Delta variant of the coronavirus. Lower courts had rejected the students’ request for an injunction while litigation continues.

       Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.