Upon his return, the Comitato Ricerche Deportati Ebrei (Committee for the Finding of Jewish Deportees) recruited Vitale to lead its research efforts. He organized housing, aid and food for the returning Jews and attended the trial of Rudolf Höß, commandant of Auschwitz, in Warsaw in 1947. Following the trial, Vitale made several visits to former concentration camp sites and began his research on Poland. In 1946, he wrote Les persécutions contre les juifs en Italie 1938–1945 (The Persecution of the Jews in Italy 1938–1945). In this report, Vitale stressed the responsibility of the Vatican and the Catholic Church in abetting and aiding the Italian Fascists. Drawing on his investigative work, he presented a list: 7496 Jews were deported from Italy and the Aegean islands and only 837 survived.