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Thomas Perlmann, secretary of the Karolinska Institute Nobel Committee and Nobel Assembly, announces Katalin Kariko and Drew Weissman as laureates of this year's Nobel Prize in Medicine during a press conference in Stockholm on Oct. 2, 2023.TOM LITTLE/Reuters

Two scientists whose work led directly to the development of mRNA vaccines used to fight COVID-19 have been awarded this year’s Nobel Prize in Physiology or Medicine.

Katalin Kariko, 68, an external consultant and former senior vice-president with the pharmaceutical company BioNTech, based in Mainz, Germany, and Drew Weissman, 64, director of vaccine research at the University of Pennsylvania, were named Nobel laureates on Monday during a live-streamed announcement at Sweden’s Karolinska Institute in Stockholm.

They will share equally in the $1.3-million prize.

Dr. Kariko and Dr. Weissman together devised a way to code messenger RNA molecules with information that allows human cells to generate viral proteins. The proteins then prime the body’s immune system, teaching it what to defend against when an infection is underway.

The Nobel is the latest and most prestigious accolade for the researchers. Since the initial rollout of mRNA vaccines by both Pfizer and Moderna, the pair have been accumulating prizes at a steady pace. Last year, they received Canada’s Gairdner International Award, together with University of British Columbia biochemist Pieter Cullis, who developed the lipid nanoparticle delivery system for the vaccines.

“The COVID pandemic stimulated scientists around the world to work to find solutions that would save the world from the enormous threat of this virus,” said Janet Rossant, president and scientific director of the Gairdner Foundation in Toronto. “Science came to the rescue with effective vaccines that have saved lives and prevented serious illness.”

While the Nobel Prize has been used to recognize some of the most important breakthroughs in biomedical research, few discoveries have reached so many people in such a short span of time.

When the COVID-19 pandemic hit in early 2020, mRNA vaccines were a new technology being developed for other applications. By the end of that year, they had become a chief defence against the pandemic and the preferred standard.

According to the latest figures from Health Canada, among those Canadians over age five who received a booster after completing their primary series of a COVID-19 vaccine, approximately 99.9 per cent received an mRNA vaccine produced by Pfizer or Moderna.

The Nobel Prize marks the culmination of a remarkable journey for Dr. Kariko, who grew up in a small village in Communist-era Hungary and dreamed of becoming a scientist.

Her pursuit of that goal led her to a PhD at the University of Szeged in 1978 and her first research position in Hungary. In 1985, she moved to Temple University in the United States and, four years later, the University of Pennsylvania, where she remains an adjunct professor of neurosurgery.

It was during this time that she became interested in the idea of using messenger RNA molecules, or mRNA, to coax human cells into creating proteins that might be used to help fight disease.

For years, Dr. Kariko gained little support for the notion and struggled with technical obstacles and a lack of funding. She did not, for example, receive a grant from the National Institutes of Health, a standard pathway for medical researchers in the United States. But she continued to pursue the idea despite a lack of recognition for its potential significance.

“This is an extraordinary and unusual scientist who was very passionate about this idea of mRNA and using it therapeutically,” said Thomas Perlmann, secretary general of the Nobel Assembly, after Monday’s announcement. “She resisted the temptation to go away from that path and do something easier.”

Things began to improve once Dr. Kariko teamed up with Dr. Weissman, a UPenn colleague, in 1997.

Dr. Weissman, a Massachusetts native who had received an MD and PhD from Boston University in 1987, had completed a fellowship at the National Institute of Allergy and Infectious Diseases, which was then under the direction of Anthony Fauci. He began to collaborate with Dr. Kariko during the same year he arrived at the UPenn to study RNA and the innate immune system.

“When I met Katie and we started talking, it seemed like the perfect union,” Dr. Weissman told The Globe and Mail last year.

Together, the two scientists realized a way to chemically alter mRNA so that it could work effectively and safely under the radar of the immune system. The key paper describing their work was published in the journal Immunity in 2005.

Sill missing was a way to get mRNA into cells, where the information it carried could be turned into proteins. That piece of the puzzle was eventually provided by Dr. Cullis, a biochemist known for his work with lipid membranes, which led to a succession of Vancouver-based companies looking to market the technology.

More developments followed as scientists became aware of their work. Among them was Derrick Rossi, a Toronto native and Harvard University biologist who in 2010 co-founded the biotech company Moderna, originally with the idea of using mRNA to treat genetic disorders.

Meanwhile, in 2013, Dr. Kariko, who still did not have a tenured position in Pennsylvania, began working with BioNTech in Germany. By 2018, a project was in the works to use mRNA as an influenza vaccine.

Then, in early 2020, the pandemic hit, creating a far more urgent need for the technology. The rest is history. The mRNA approach – advanced by the pharma giant Pfizer in partnership with BioNTech, and separately by the Massachusetts-based company Moderna – were the first effective COVID-19 vaccines authorized for human use in Canada and the U.S.

So timely was the arrival of the vaccines that some skeptics questioned how such an astonishing development could have been made apparently overnight. When asked by The Globe and Mail last year how she responded to such an assessment of her 40-year journey to the vaccine, Dr. Kariko responded: “It took a zillion overnights.”

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