Omicron v Delta: Which is more likely to lead to long Covid?

The researchers, who published their findings in the medical journal The Lancet, revealed just under five per cent of people infected with Omicron went on to develop long Covid, compared to almost 11 per cent of Delta cases. The Omicron variant spread quickly across the world after it was first detected in November, 2021. And while Omicron appears to cause less severe acute illness than previous variants, at least in vaccinated populations, the potential for people to experience long-term symptoms was a major concern, the researchers wrote.“We believe this is the first peer-reviewed study to report on long Covid risk associated with infection by the Omicron variant, highlighting that health surveillance using smartphone apps can produce rapid insights, which we have consistently shown are accurate and subsequently replicated,” they wrote.The researchers collected data from patients who had new or ongoing symptoms four weeks or more after the start of acute Covid-19 in the UK during the Omicron period and compared it with the Delta period. They used self-reported data from the UK’s Covid Symptom Study appThey identified 56,003 UK adults who first tested positive between December 20, 2021, and March 9, 2022, and satisfied the inclusion criteria for the Omicron strain. NED-6477-Omicron-family-treeUsing identical selection criteria, 41,361 adult cases of the Delta were identified between June 1, 2021, and November 27, 2021.Among Omicron cases, 2501 (4·5 per cent) of people experienced long Covid and, among Delta cases, 4469 (10·8 per cent) experienced long Covid.Dr David Strain, Clinical Senior Lecturer and Honorary Consultant, University of Exeter Medical School, said the results were “very reassuring for people who caught Covid in that (the Omicron) period.” However he said it might not apply to all strains of the Omicron variant.“It is important to say however that these data come from the omicron BA. 1 period,” he said. “The Office for National Statistics suggested that the BA. 2 variant that has caused much of the recent wave, did cause long Covid in triple-vaccinated people at approximately the same rate as the Delta.”Dr Strain said it was impossible to comment on the longer term impact of these variants as it was still early days. “However even 4.4 per cent of the very large number who experienced Covid as protections were eased, creates a significant public health burden of this disease with no known treatment, or even reliable diagnostic test,” he said.