The 2019 Nobel Prize for Medicine has been jointly awarded to William Kaelin Jr., Sir Peter Ratcliffe and Gregg Semenza for their pioneering research into how human cells respond to changing oxygen levels.

Announcing the prize at the Karolinska Institute in Stockholm on Monday, the Nobel committee said that the trio's discoveries have paved the way for "promising new strategies to fight anaemia, cancer and many other diseases."

The 2019 medicine laureates, the committee added, have identified molecular machinery that regulates the activity of genes in response to varying levels of oxygen.

The importance of oxygen has long been established, the committee explained, but how cells adapt to changes in its levels remained unknown.

Randall Johnson, prize committee member, described the trio's work as a "textbook discovery."

"This is something basic biology students will be learning about when they study, at aged 12 or 13, or younger, biology and learn the fundamental ways cells work. This is a basic aspect of how a cell works and, from that standpoint alone, it's a very exciting thing."

The winners

New York-born Kaelin established his own research laboratory at the Dana-Farber Cancer Institute in Boston and became a full professor at Harvard Medical School in 2002.

Semenza, also born in New York, became a full-time professor at Johns Hopkins University in 1999 and since 2003 has been the Director of the Vascular Research Program at the Johns Hopkins Institute for Cell Engineering.

Ratcliffe, who was born in Lancashire, England, studied medicine at Cambridge University and established an independent research group at Oxford University, becoming a full professor in 1996.