Pope Francis entered his fourth week in hospital with double pneumonia on Saturday, increasingly handing off his day-to-day duties.

Francis is said to be responding well to treatment and has shown a ‘gradual, slight improvement’, his doctors say.

The pope's health was the prime focus of the Mass, celebrated by Cardinal Christophe Pierre, the Vatican nuncio to the United States.

The Vatican issued a medical update saying Pope Francis' prognosis remains "guarded," but he is "alert" and even joking with visitors.

The Vatican says Pope Francis is responding well to therapy for double pneumonia and has shown a “gradual, slight improvement” in recent days.

Pope Francis was on the minds of everyone who came to mass at St. Charles Borromeo Catholic Church in North Hollywood Sunday morning, including Cardinal Roger Mahony.