Pope Francis marked the 12th anniversary of his papacy Thursday with increasingly positive medical updates four weeks into his hospitalization for double pneumonia.

The pope spent another tranquil night, the Vatican said in its brief morning statement.

A chest X-ray confirmed improvements, the Vatican said on Wednesday, just two days after doctors declared he's no longer in imminent danger of death. The latest medical bulletin said that the 88-year-old pope's condition remained stable, but indicated a complex picture considering his overall fragility.

The Holy See hasn't said how the anniversary of his election as the 266th pope might be commemorated. It is a public holiday at the Vatican and masses are planned in his honor at churches in Rome. No medical bulletins will be issued.

Francis on Wednesday remotely followed a Lenten spiritual retreat that has been a mainstay of his papacy. He continues to receive high flows of oxygen through nasal tubes during the day and a non-invasive mechanical mask to aid his rest at night.

The former Cardinal Jorge Mario Bergoglio was elected on the fifth ballot of the 2013 conclave, which was called after Pope Benedict XVI resigned.

While Francis has praised Benedict's humility in stepping down and said he might follow in his footsteps, more recently he has said the papacy is a job for life.

Another milestone comes Friday, when Francis marks four weeks of hospitalization.