The SARS-CoV-2 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 (June 18, 2022) in a letter to the medical journal 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 the 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.
Reduced Odds, But Higher Absolute Numbers
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 9, 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 number of people infected with Omicron from December 2021 to February 2022. The UK Office of National Statistics estimated the number of people with long COVID actually increased from 1.3 million in January 2022 to 2 million as of May 1st, 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.”
Reference: “Risk of long COVID associated with delta versus omicron variants of SARS-CoV-2” by Michela Antonelli, Joan Capdevila Pujol, Tim D Spector, Sebastien Ourselin and Claire J Steves, 18 June 2022, The Lancet.
DOI: 10.1016/S0140-6736(22)00941-2
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