WASHINGTON — Supreme Court Justice Amy Coney Barrett on Thursday refused to block a plan by Indiana University to require students and employees to get vaccinated against COVID-19.Barrett’s action came in response to an emergency request from eight students and marked the first time the high court has weighed in on a vaccine mandate. Some corporations, states and cities have adopted vaccine requirements for workers or even to dine indoors, and others are considering doing so.The students said in court papers …