Pope Francis has spent a fourth night hospitalized in Rome, where he is being treated for a respiratory tract infection.

In recent weeks, the 88-year-old pope has spoken out against the Trump administration’s anti-immigrant policies. In a letter to U.S. bishops, the pope wrote, “The act of deporting people who in many cases have left their own land for reasons of extreme poverty, insecurity, exploitation, persecution or serious deterioration of the environment, damages the dignity of many men and women, and of entire families, and places them in a state of particular vulnerability and defenselessness.”