President Joe Biden is commuting the sentences of roughly 1,500 people who were released from prison and placed on home confinement during the coronavirus pandemic and is pardoning 39 Americans convicted of nonviolent crimes. It’s the largest single-day act of clemency in modern history.

The commutations announced on Thursday are for people who have served out home confinement sentences for at least one year after they were released. Prisons were uniquely bad for spreading the virus and some inmates were released in part to stop the spread. At one point, 1 in 5 prisoners had COVID-19.