Study: Omicron less likely than Delta to cause long COVID

June 16 (UPI) -- The Omicron variant of COVID-19 is less likely than the Delta variant to cause long COVID, according to King's College of London data published Thursday.

In the first peer-reviewed study on long COVID risk and the Omicron variant, researchers said the odds of getting long COVID from Omicron were 20-50% less than with the Delta variant.

Researchers found that 4.4% of Omicron cases resulted in long COVID while 10.8% of Delta cases became long COVID. The study compared 56,003 adult cases in Britain during the period when Omicron was dominant variant versus 41,361 when Delta was dominant.

"The Omicron variant appears substantially less likely to cause Long-COVID than previous variants but still 1 in 23 people who catch COVID-19 go on to have symptoms for more than four weeks," study lead author Dr Claire Steves said.

Long COVID is defined as having ongoing or new symptoms including fatigue, shortness of breath, loss of concentration and joint pain.

The study said absolute numbers of long COVID were higher during the Omicron period due to the vastly higher number of people infected with Omicron during the study period.

The U.K. Office of National Statistics estimated the numbers of people with long COVID increased from 1.3 million in January 2022 to 2 million as of May 1, 2022.

The King's College London study was published in a letter to The Lancet.