Long COVID risk less after Omicron infection compared to infection by Delta varient: LANCET

The Omicron variant is less likely to cause long COVID than the Delta variant, new research has found.

Analysis by researchers from King's College London of data from the ZOE COVID Symptom study app is published today in a letter to The Lancet. The findings are from the first peer-reviewed study to report on long COVID risk and the Omicron variant.

Long COVID is defined by NICE guidelines as having new or ongoing symptoms four weeks or more after the start of disease. Symptoms include fatigue, shortness of breath, loss of concentration and joint pain. The symptoms can adversely affect day-to-day activities, and in some cases can be severely limiting.

Researchers found the odds of experiencing long COVID were between 20-50% less during the Omicron period versus the Delta period, depending on age and time since vaccination.

The study identified 56,003 UK adult cases first testing positive between December 20 2021 and March 9th 2022 when Omicron was the dominant strain. Researchers compared these cases to 41,361 cases first testing positive between June 1 2021 and November 27 2021 when the Delta variant was dominant.

The analysis shows 4.4% of Omicron cases were long COVID, compared to 10.8% of Delta cases. However, the absolute number of people experiencing long COVID was in fact higher in the Omicron period. This was because of the vast numbers of people infected with Omicron from December 2021 to February 2022. The UK Office of National Statistics estimated the numbers of people with long COVID actually increased from 1.3 million in January 2022 to 2 million as of 1st May 2022.

Lead author, Dr Claire Steves from King's College London, said: "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. Given the numbers of people affected it's important that we continue to support them at work, at home and within the NHS."