(CNN) -- In a first for the prestigious organization, a Nobel Prize will go to a man who died just days before being named a winner.
Ralph Steinman, a biologist with Rockefeller University, was named a winner Monday of the 2011 Nobel Prize in Physiology or Medicine. He would have won half the prize of approximately $1.5 million; the other half will be shared by scientists Bruce A. Beutler and Jules A. Hoffmann.
Steinman died of pancreatic cancer Friday at the age of 68, after having extended his life using a kind of therapy he designed, his university said in a statement Monday.
The Nobel committee was unaware of his death. Had they known, their own rules would have precluded him being selected as a winner. The decision was made Monday, just before the announcement, Nobel officials said.
"The events that have occurred are unique and, to the best of our knowledge, are unprecedented in the history of the Nobel Prize," the Nobel Assembly said in a statement, announcing that Steinman will remain a Nobel laureate.
Making the decision meant circumventing one of the Nobel rules.
The Nobel Prize website states that since 1974, rules have stipulated that a prize "cannot be awarded posthumously, unless death has occurred after the announcement."
In its statement Monday, the Nobel Assembly said it interpreted "the purpose of the rule" as making sure no one is "deliberately" awarded the prize posthumously. Because the committee did not know of Steinman's death, the decision "was made in good faith," the assembly said.
The Nobel committee also expressed "deep sadness and regret" at the news.
Speaking to CNN, Goran Hansson, secretary-general of the Nobel assembly overseeing the Nobel Prize in Physiology or Medicine, said the fact that Steinman didn't know he would win "adds to the sadness."
Hansson said that after the committee chose the winners Monday, he tried to call Steinman to inform him of the good news.
Rockefeller University said Steinman "discovered the immune system's sentinel dendritic cells and demonstrated that science can fruitfully harness the power of these cells and other components of the immune system to curb infections and other communicable diseases."
"He was diagnosed with pancreatic cancer four years ago, and his life was extended using a dendritic cell-based immunotherapy of his own design," the university said in a statement.
The Nobel committee noted Steinman's "discovery of the dendritic cell and its role in adaptive immunity."
Bruce A. Beutler and Jules A. Hoffmann won "for their discoveries concerning the activation of innate immunity."
In 1996, William Vickrey died days after the announcement that he had won the Nobel Prize in economics.
Before 1974, two people received Nobel Prizes posthumously -- Dag Hammarskjold won the Nobel Peace Prize in 1961, and Erik Axel Karlfeldt won for literature in 1931.
Monday's announcement about the winners kicked off a week of awards that will also honor achievements in physics, chemistry, literature, peace and economics.
The Nobel Assembly at Karolinska Institute said Beutler, Hoffmann and Steinman have "revolutionized our understanding of the immune system by discovering key principles for its activation."
"Bruce Beutler and Jules Hoffmann discovered receptor proteins that can recognize such microorganisms and activate innate immunity, the first step in the body's immune response," the committee said in a written statement. "Ralph Steinman discovered the dendritic cells of the immune system and their unique capacity to activate and regulate adaptive immunity, the later stage of the immune response during which microorganisms are cleared from the body."
The Nobel laureates' discoveries and work have opened up new opportunities for the development of prevention and therapy against infections, cancer and inflammatory diseases, the committee said.
The prize in medicine, worth 10 million Swedish kronor (about $1.5 million), went last year to Robert G. Edwards, "the father of the test tube baby."
Since the first birth from in vitro fertilization in 1978, Edwards' work has led to the birth of about 4 million babies, the awards committee said in praising his work.
On Tuesday, the committee will announce its award for achievement in physics. The next day, the winner of the Nobel Prize in chemistry will be announced.
The committee will announce the most anticipated of the annual honors -- the Nobel Peace Prize -- on Friday.
On October 10, the committee will announce its award for the prize for economics.
Since 1901, the committee has handed out the Nobel Prize in Physiology or Medicine 101 times. The youngest recipient was Frederick G. Banting, who won in 1923 at the age of 32. The oldest medicine laureate was Peyton Rous, who was 87 years old when he was awarded the prize in 1966.