Pope John Paul's health dramatically worsened Friday, and millions of Catholics around the world are praying for the 84-year-old pontiff, who has led the church for 26 years. Vatican officials held a special prayer service in St. Peter's Square, where one official said "Christ is opening the door to the pope this evening or tonight." Earlier Mass was celebrated in a Rome basilica. Tens of thousands of people packed the square outside the Pope's window in an all-night prayer vigil. The Vatican said Friday the pope's condition had deteriorated, his heart and kidneys were failing, and his breath had become shallow. A Vatican spokesman said the pope was conscious, serene, and declined to go to the hospital. The spokesman said the pontiff had suffered a "cardio-circulatory collapse" after developing a high fever from a urinary tract infection. The Polish-born pontiff -- the first non-Italian to serve as pope in 450 years -- suffers from Parkinson's disease and a number of other health problems. He underwent a procedure in February to ease breathing difficulties.