London, Mar 10 (IANS): The Omicron variant of SARS-CoV-2 is much less likely to lead to long Covid than the variant circulating at the start of the Covid-19 pandemic, new research shows.

The study found that healthcare workers infected with the original wild-type virus were up to 67 per cent more likely to report symptoms of long Covid than those who hadn't had Covid-19.

However, people who were first infected with the Omicron variant were no more likely to report long Covid symptoms than those who'd never had Covid-19.

The research also found that having Omicron after a wild-type infection does not carry a greater risk of long Covid or fatigue than having a wild-type infection alone.

Further, the analysis also revealed that re-infection -- an Omicron infection after a wild-type infection -- didn't carry a greater risk of long Covid or fatigue than a wild-type infection alone.

Similarly, vaccination did not affect the risk of long Covid or fatigue in those who had Omicron after the wild-type virus.

While the reason remains unclear, the researchers speculated that "it's probably due to a combination of the Omicron variant being less likely to cause severe illness than the wild-type virus -- we know that long Covid is more common after severe illness -- and immunity acquired through previous exposure to the virus through, for example, a subclinical infection without seroconversion", according to Dr Carol Strahm, of the Division of Infectious Diseases and Hospital Epidemiology, Cantonal Hospital St Gallen, in Switzerland.

"Long Covid is a significant public health issue with prolonged, sometimes debilitating, illness, limited treatment options and uncertain outcome," Dr Strahm added, noting that "it is vital to find out more about who is at risk of long Covid and why."

For the study, the team assessed rates of long Covid symptoms in 1,201 healthcare workers infected with the wild-type SARS-CoV-2 virus, the omicron variant (BA.1) or both and compared these to uninfected controls.

The participants, who were recruited between June and September 2020, underwent regular testing for Covid-19 (nasopharyngeal swabs and antibody tests) and provided information on their vaccination status till June 2022.

The findings will be presented at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID 2023) scheduled to be held in Copenhagen in April.