Pope Francis has made a surprise appearance in St Peter’s Square during a special jubilee mass for the sick and health workers, marking his first public appearance at the Vatican since his discharge from hospital two weeks ago.

The pontiff waved at the crowd that stood and applauded as he was appeared unannounced, assisted in a wheelchair to the front of the altar in the square.

“Good Sunday to everyone,’’ Francis said, speaking into a microphone, which he tapped to make sure it was working on a second attempt. “Thank you very much.”

The pontiff’s voice sounded stronger than when he addressed wellwishers outside Gemelli hospital on the day of his release on 23 March, after being diagnosed with life-threatening pneumonia during a five-week hospital stay. He has just completed two weeks of at least two months of doctor-ordered rest as he continues physical, respiratory and speech therapy, as well as treatment for a lingering lung infection.

The pope referred to his experience with illness in both the traditional Sunday blessing and the homily read by Archbishop Rino Fisichella, the organiser of the Holy Year, which is expected to bring 30 million pilgrims to Rome.

Addressing the sick among the crowd, the pope said in the homily read by Fisichella that “in this moment of my life I share a lot: the experience of infirmity, feeling weak, depending on the others for many things, needing support.

“It is not easy, but it is a school in which we learn every day to love and to let ourselves be loved, without demanding and without rejecting, without regretting, without despairing, grateful to God and to our brothers for the good that we receiev, trusting for what is still to come.”

He also urged the faithful not to push the fragile from their lives “as unfortunately a certain mentality does today. Let’s not ostracise pain from our surroundings. Let’s instead make it an opportunity to grow together, to cultivate hope.”

In the traditional Sunday blessing, he offered prayers for doctors, nurses and health care workers “who are not always helped to work in inadequate conditions, at times the victims of aggression. Their mission is not easy and must be supported and respected.”