Pope Francis issued a message Sunday thanking volunteers for the “miracle of tenderness” they offer the sick, as the Vatican celebrated the Holy Year Mass for volunteers around the world in his absence.

After more than three weeks in the hospital recovering from double pneumonia, the 88-year-old pope’s doctors reported positive news about his health over the weekend, saying Francis was responding well to treatment and has shown a “gradual, slight improvement” in recent days.

For the fourth Sunday in a row, the 88-year-old Francis didn’t appear for his weekly noon blessing, but he met with his top deputies and the Holy See distributed the text he would have delivered if he were well enough. In it, the Argentine pope thanked all those who were caring for him and others who are sick and experiencing a “night of pain.”

“Brothers and sisters, during my prolonged hospitalization here, I too experience the thoughtfulness of service and the tenderness of care, in particular from the doctors and health care workers, whom I thank from the bottom of my heart,” read the message from Gemelli hospital.

“And while I am here, I think of the many people who in various ways are close to the sick, and who are for them a sign of the Lord’s presence. We need this, the ‘miracle of tenderness’ which accompanies those who are in adversity, bringing a little light into the night of pain,” he wrote.

Francis, who has chronic lung disease and had part of one lung removed as a young man, has remained in stable condition at Gemelli, with no fever and good oxygen levels in his blood for several days, doctors reported in a Vatican statement Saturday.

The doctors said that such stability “as a consequence testifies to a good response to therapy.” It was the first time the doctors had reported that Francis was responding positively to the treatment for the complex lung infection that was diagnosed after he was hospitalized on Feb. 14. The positive update for Francis followed a few bouts of respiratory crises last week.

Doctors characterized the pope’s prognosis as “guarded,” meaning he’s not out of danger.

“In order to record these initial improvements in the coming days as well, his doctors have prudently maintained the prognosis as guarded,” the Vatican said in a statement.

On Sunday morning, the Vatican reported Francis was resting after a quiet night. 

In his absence, the Vatican’s day-to-day operations continued alongside celebrations of its Holy Year, the once-every-quarter-century Jubilee that brings millions of pilgrims to Rome. On Sunday, Canadian Cardinal Michael Czerny, who is close to Francis, celebrated the Holy Year Mass for volunteers that Francis was supposed to have celebrated.

During the Mass in St. Peter’s Square, the giant banner bearing Francis’ papal coat of arms fluttered from the loggia of the basilica above. Even while in the hospital, Francis is very much still the pope and in charge of the Catholic Church.

That was evident too by the fact that the Vatican secretary of state, Cardinal Pietro Parolin, and chief of staff, Archbishop Edgar Pena Parra, visited the pope on Sunday, for the third time since he has been in the hospital. The Vatican has noted that such meetings are the routine way the pope governs while at the Vatican, making clear that he was getting essential work done from Gemelli.

Francis has been using high flows of supplemental oxygen to help him breathe during the day and a noninvasive mechanical ventilation mask at night.

Francis was hospitalized Feb. 14 for what was then just a bad case of bronchitis. The infection progressed into a complex respiratory tract infection and double pneumonia that has sidelined Francis for the longest period of his 12-year papacy and raised questions about the future.