(CNN) — Pope Francis showed a “clear improvement” on Thursday after being given intravenous antibiotics for a bronchitis infection and could be released from the hospital in the next few days, according to the Vatican.

The 86-year-old pontiff, who as a young man had a small part of his right lung removed, was admitted to Rome’s Gemelli hospital on Wednesday after complaining of breathing problems. Following clinical checks and tests, the doctors identified that he had bronchitis and were administering antibiotic therapy to treat him.

“Based on the predictable outcome, the Holy Father could be released in the next few days,” Vatican spokesman Matteo Bruni said in a statement, adding that Francis had spent the afternoon resting, praying and carrying out some work.

“His Holiness Pope Francis rested well during the night. The clinical picture is progressively improving and the planned treatments continue. This morning after breakfast, he read some newspapers and went back to work,” Bruni said.

“Before lunch he went to the little chapel of the private apartment, where he gathered in prayer and received the Eucharist.”

The pontiff has acknowledged the many well-wishes he has received while in the hospital on Twitter. Francis said: “I am touched by the many messages received in these hours and I express my gratitude for the closeness and prayer.”

After his weekly general audience in St. Peter’s Square on Wednesday, the pontiff was taken to the hospital to undergo a number of tests. Earlier in the day, the Vatican had said that the visit and tests were planned.

“The Holy Father has been at Gemelli since this afternoon for some previously scheduled tests,” Bruni had said.

Shortly after, he said that Francis’ schedule for Thursday had been cleared “to make space for the continuation of tests should that be necessary.”

Vatican sources told CNN Thursday that Pope Francis “slept well” during his first night in the hospital.

The Church of Rome also expressed “all its closeness and affection to its Bishop Pope Francis, and ensures its unceasing prayers, wishing him a speedy recovery,” it said in a statement on Thursday.

Bishops in churches across Italy are praying for Francis’ speedy recovery, the Presidency of the Italian Episcopal Conference, on behalf of the Italian bishops, said in a statement on Wednesday.

“In wishing the Holy Father a speedy recovery, the Presidency entrusts to the Lord the doctors and medical staff who, with professionalism and dedication, care for him and all patients,” it added.

The pontiff — who as a young man suffered from severe pneumonia and had part of a lung removed — has had a recent history of medical issues.

He has often been seen with a walking stick and sometimes uses a wheelchair due to pain in his right knee. Last year, he canceled a trip to Democratic Republic of Congo and South Sudan after doctors said he might also have to miss a later trip to Canada unless he agreed to have 20 more days of therapy and rest for his knee. He ultimately went to the DRC and South Sudan in February.

Francis also suffers from diverticulitis, a common condition that can cause the inflammation or infection of the colon. In 2021, he had surgery to remove part of his colon.

In December, Francis revealed that he had already signed his resignation letter to be used in the event of him becoming “impaired.” Francis made the comment in an interview with Spanish news outlet ABC when asked what would happen if a pope is suddenly rendered unable to perform his duties due to health issues or an accident.

Francis said he wrote the letter several years ago and gave it to then-Vatican Secretary of State Cardinal Tarcisio Bertone, who resigned in 2013.

“I have already signed my renunciation. The Secretary of State at the time was Tarcisio Bertone. I signed it and said: ‘If I should become impaired for medical reasons or whatever, here is my renunciation,'” Francis was quoted as saying, adding that this was the first time he had spoken publicly about the letter’s existence.

Francis said past pontiffs Paul VI and Pious XII had also drafted their letters of renunciation in the event of a permanent impairment.

In 2013, Francis’ immediate predecessor, Pope Benedict XVI, made the almost unprecedented decision to resign from his position, citing “advanced age” as the reason and startling the Catholic world.

It marked the first time a pope had stepped down in nearly 600 years. The last pope to step down before his death was Gregory XII, who in 1415 quit to end a civil war within the church in which more than one man claimed to be pope.

Pope showing ‘clear improvement’ after antibiotic treatment for bronchitis infection, could leave hospital soon