London, Jun 17 (IANS): The Omicron variant is less likely to cause long Covid than the Delta variant, according to new research published in a letter to The Lancet.

Long Covid is defined 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 from King's College London analysed data from the ZOE Covid Symptom study app and found the odds of experiencing long Covid were between 20-50 per cent 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 per cent of Omicron cases were long Covid, compared to 10.8 per cent 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 researchers 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," said lead author Dr Claire Steves from King's College London.

"Given the numbers of people affected it's important that we continue to support them at work, at home and within the NHS," Steves added.