The Nobel Prize in Physiology or Medicine has been awarded to a pair of scientists who developed the technology that led to the mRNA Covid vaccines.
Dr Katalin Kariko and Dr Drew Weissman will share the prize.
The technology was experimental before the pandemic, but has now been given to millions of people around the world.
The same mRNA technology is now being researched for other diseases, including cancer.
The Nobel Prize Committee said: "The laureates contributed to the unprecedented rate of vaccine development during one of the greatest threats to human health in modern times."
Vaccines train the immune system to recognise and fight threats such as viruses or bacteria.
Traditional vaccine technology has been based on dead or weakened versions of the original virus or bacterium - or by using fragments of the infectious agent.
In contrast, mRNA vaccines used a completely differently approach.
During the Covid pandemic, the Moderna and Pfizer/BioNTech vaccines were both based on mRNA technology.
Drs Kariko and Weissman met in the early 1990s when they were working at the University of Pennsylvania in the US.
