Macchiarini, famed for his pioneering use of stem cells in regenerative surgery, was reported to the Swedish authorities by four doctors as early as 2014. But an internal probe cleared him of research misconduct and carrying out procedures without ethical permission.
However, after a documentary by Swedish broadcaster SVT sparked debate when it shed light on some of his more controversial surgeries, the hospital ordered Kjell Asplund, chairman of the Swedish National Council on Medical Ethics, to carry out an external investigation.
"Much went wrong in connection with Macchiarini's transplants of synthetic trachea," said Asplund in a statement when he presented the results of the inquiry on Wednesday.
"Macchiarini should not even have been employed at the hospital. There were shortcomings in how the decisions about the transplants were made and how they acted on existing laws. The hospital has a big task ahead to ensure patient safety and trust."
At a press conference Asplund elaborated: "Hospitals where he had performed surgeries before gave him strongly negative reviews. These critical voices were not taken into account. There was never a job interview, for example. Our conclusion is that the hospital needs a better hiring process."
Kjell Asplund at Wednesday's press conference. Photo: Stina Stjernkvist/TT
The Italian celebrity surgeon rose to fame in 2011 for carrying out the first synthetic organ transplant, making a trachea – or windpipe – from plastic, and using it as a frame into which the patient's own stem cells could then grow.
Three of these were carried out at Karolinska University Hospital. However, two of the patients later died and one was forced to have a new transplant in the US.
Asplund said that all three patients had been seriously ill and that in two of the cases the cancer types had been so unusual that it was impossible to determine the extent of their illness. But he added that there had not been "an immediate life threat" in either of the cases when the transplants were carried out.
Discussing what would have happened had the transplantations not been carried out, the report states: "Progressing cancer in two of the patients would very likely have led to death on the longer term. In the third patient, complications of her tracheal injury, especially severe infections, entailed a significant threat to life."
Karolinska bosses said later on Wednesday that the hospital would now be looking into another four cases involving Macchiarini to see if there had been any complications or wrongdoing.
"What has happened is both unacceptable and exceptional and we apologize to those who have been affected and their families. A number of mistakes were made and we did not respect laws and regulations, which is unacceptable. In the coming weeks we're going to look at how it happened," hospital director Melvin Samsom said at a press conference.
Samsom and head physician Nina Nelson Follin. Photo: Stina Stjernkvist/TT
Asplund's report also states that the three operations should have undergone an ethical review, and would likely not have been given approval had they done so.
"Our collective assessment is that there was not an adequate scientific foundation for a human transplant of a synthetic trachea seeded with bone marrow cells, combined with the application of growth-stimulating drugs. The concept conflicted not only with scientific and proven experience; it was also too early to conduct a scientific study on humans," it reads.
The scandal has grabbed headlines worldwide and has been described as an "ethical Chernobyl" for the medical institution. Asplund said it had also damaged Sweden's reputation in the field of clinical research.
Macchiarini is the subject of nearly a dozen separate ongoing inquiries, including five at the Karolinska Institute (KI), which is closely linked to the hospital, and a police investigation into suspected manslaughter.
He is also accused of having lied on his CV when he applied for a position at KI, from where he was fired in March following the allegations.