Pope Francis' doctors on Monday lited a "guarded prognosis" though he will need to remain in the "hospital setting for a period of time" in the treatment of double pneumonia, the Vatican said.

The 88-year-old pope has remained stable, with no fever and good oxygen levels in his blood for several days, doctors said.

Pope Francis is responding well to the treatment for double pneumonia and has shown a "gradual, slight improvement" in recent days, the Vatican said Saturday. But his doctors have decided to keep his prognosis as guarded, meaning that he's not out of danger yet.