Hungarian scientist Katalin Kariko and her U.S. research partner Drew Weissman won this year's Nobel Prize in physiology or medicine on Monday for their work leading to the development of COVID-19 vaccines using a new messenger RNA technology, the Nobel Assembly at the Karolinska Institute said.

Kariko and Weissman, who are professors at the University of Szeged in Hungary and the University of Pennsylvania in the United States, respectively, found ways to engineer mRNA molecules so they could get into human cells without triggering an inflammatory response, enabling their use as a vaccine.

"The discoveries by the two Nobel laureates were critical for developing effective mRNA vaccines against COVID-19 during the pandemic that began in early 2020," the assembly said, hailing their findings as "groundbreaking."

Photo of scientists Katalin Kariko and Drew Weissman are shown on a screen during the announcement of the Nobel Prize in physiology or medicine in Stockholm on Oct. 2, 2023. (picture alliance/Getty/Kyodo)

"The laureates contributed to the unprecedented rate of vaccine development during one of the greatest threats to human health in modern times," it added in the statement.

Kariko, 68, also adjunct professor at the University of Pennsylvania, said she was sleeping at her home in a suburb of Philadelphia when she received a call about the award and thought somebody was "joking," according to an audio record of an interview that was made available by the Swedish award-giving body.

Weissman, 64, said in a separate audio recording that it was "always a dream" for him to win the prize, but he had not thought it would actually happen.

While vaccine development usually requires some 10 years, their findings have helped cut down the time for the practical application of vaccines to around one year from the pandemic's start.

Based on the technology, effective mRNA vaccines against COVID-19 have been developed by U.S. pharmaceutical giant Pfizer Inc. and its German partner BioNTech SE, as well as U.S. biotechnology firm Moderna Inc.

Kariko was senior vice president at BioNTech before becoming an external consultant of the company.

Katalin Kariko (L) and Drew Weissman are pictured in Tokyo in April 2022. (Kyodo)

Traditional vaccines have put a weakened or inactivated germ into human bodies to trigger an immune response, but mRNA vaccines give instructions for cells to make a harmless "spike protein" that resembles one found in the novel coronavirus.

The immune system then detects the protein and starts building an immune response, making antibodies to protect against future infection.

Kariko and Weissman, as University of Pennsylvania colleagues, began investigating mRNA as a potential therapeutic after a chance meeting in the late 1990s while photocopying research papers, according to the university's press release.

Starting in 2005, Kariko and Weissman published studies that "eliminated critical obstacles on the way to clinical applications of mRNA," with inflammatory response almost abolished by modifying mRNA, the Nobel Assembly said.

The impressive flexibility and speed with which mRNA vaccines can be developed also pave the way for using the new platform also for vaccines against other infectious diseases, the assembly said.

In the future, the technology may also be used to deliver therapeutic proteins and treat some cancer types, it said.

The two winners will receive joint prize money of 11 million Swedish kronor ($1 million), with an award ceremony held in Sweden on Dec. 10.

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