The 2023 Nobel Prize in Physiology or Medicine has been awarded to Katalin Kariko of Hungary and Drew Weissman of the United States "for their discoveries concerning nucleoside base modifications that enabled the development of effective mRNA vaccines against COVID-19," the Nobel Assembly at Sweden's Karolinska Institute announced on Monday.

The prize, among the most prestigious in the scientific world, is selected by the Nobel Assembly of Sweden's Karolinska Institute medical university and comes with 11 million Swedish crowns (about $1 million).

"So this year's Nobel Prize recognizes their basic science discovery that fundamentally changed our understanding of how mRNA interacts with the immune system and had a major impact on society during the recent pandemic," said Rickard Sandberg, member of the Nobel Assembly at Karolinska Institute.

Kariko was senior vice president and head of RNA protein replacement at BioNTech until 2022 and has since acted as an adviser to the company. She is also a professor at the University of Szeged in Hungary and an adjunct professor at the University of Pennsylvania's Perelman School of Medicine.

Co-winner Weissman is professor in vaccine research, also at Pennsylvania. "It's an incredible honor," he said. "We couldn't have come to the result without both of us being involved."

The two laureates in 2005 jointly developed nucleoside base modifications, which stop the immune system from launching an inflammatory attack against lab-made mRNA, previously seen as a major hurdle against any therapeutic use of the technology.

BioNTech said in June that about 1.5 billion people across the world had received its mRNA shot, co-developed with Pfizer. It was the most widely-used shot in the West.

Before COVID-19 vaccine research

Having grown up in a village in a house without running water or a refrigerator, Kariko got a biochemistry doctorate in Szeged before she and her husband sold their Soviet-made Lada car, sewed the money into their daughter's teddy bear and went to the U.S. on a one-way ticket.

The daughter, Susan Francia, became a U.S. national rower and Olympic gold winner.

At the University of Pennsylvania, Kariko tried to turn mRNA into a treatment tool throughout the 1990s but struggled to win grants because work on DNA and gene therapy captured most of the scientific community's attention at the time.

Kariko has said she endured ridicule from fellow faculty members for her dogged pursuit, which led to her demotion. Taunting continued, she said, when she joined BioNTech in 2013 because the firm did not even have a website at the time.

Weissman received his doctorate from Boston University in 1987 and joined the University of Pennsylvania in 1997.

The two have said they met in 1998 while waiting for rationed photocopying machine time. The ensuing chat piqued immunologist Weissman's interest in Kariko's RNA work. 

"It is absolutely right that the ground-breaking work on RNA led by Kariko and Weissman should be recognised by a Nobel Prize," said Sir Andrew Pollard, an immunology professor at Oxford University, who pursued a different technology when co-developing the lesser-used COVID vaccine by AstraZeneca.

Nobel Prize

The medicine prize kicks off this year's awards, with the remaining five set to be unveiled in the coming days.

The prizes, first handed out in 1901, were created by Swedish dynamite inventor and wealthy businessman Alfred Nobel and are awarded for achievements in science, literature and peace, and in later years also for economics.

The Swedish king will present the prizes at a ceremony in Stockholm on December 10, the anniversary of Nobel's death, followed by a lavish banquet at city hall.

Last year's medicine prize went to Swede Svante Paabo for sequencing the genome of the Neanderthal, an extinct relative of present-day humans, and for discovering a previously unknown human relative, the Denisovans.

Other past winners include Alexander Fleming, who shared the 1945 prize for the discovery of penicillin, and Karl Landsteiner in 1930 for his discovery of human blood groups.

(With input from agencies)