Study shows long COVID symptoms resolve for most

Among a cohort of people who contracted COVID-19 during Australia’s first wave in 2020, most signs of long COVID had disappeared by two years later, new research from the Kirby Institute has found.
 
Published in Nature Communications, the study examined immune responses and health-related quality of life measures in people who were infected with ‘mild-to-moderate’ COVID-19.
 
Results showed that biomarkers for long COVID present in those at eight months were largely resolved by 24 months for nearly two in three (62%) study participants.
 
The paper forms part of the ADAPT study, an ongoing observational study collecting details on people’s symptoms at regular intervals after SARS-CoV-2 infection, using a combination of self-reported health information and detailed laboratory analyses of bloods.
 
As well as tracking people who contracted COVID-19 during Australia’s first wave, the ADAPT study  followed a matched control group for up to two years, demonstrating in early 2022 that long COVID symptoms are consistent with biomarkers showing ‘a sustained inflammatory response’ at eight months following infection, confirming the differences of long COVID to other infections.
 
In the latest study, there were ‘no observable differences’ between the group with long COVID and the control group after 24 months, compared to ‘marked differences’ in both groups at eight months. The laboratory data trend was also found in the self-reported responses, with 62% reporting improvements in health-related quality of life.
 
Dr Chansavath Phetsouphanh, lead author and senior lecturer at the Kirby Institute welcomed the latest ADAPT results.
 
‘Almost one and a half years later, we are pleased to see that among this same group, significant improvements were found in blood markers,’ he said.
 
‘For the majority of samples we analysed in the laboratory, the biomarkers previously indicating abnormal immune function have resolved.’
 
The authors state their findings provide ‘optimistic insights’ that long COVID abnormalities can resolve over time, and are important for ‘continuing to define the natural history of this new condition’.
 
The study is one of many underway investigating the various long-term impacts of COVID-19, how it is diagnosed, and how it is treated.
 
However, while the ADAPT findings are encouraging, the authors note they are based on just one cohort who experienced an early strain of COVID-19.
 
‘Immunology is a complex science, and it is impossible to say for certain that outcomes in our unvaccinated clinical cohort will be true for vaccinated people or for people who may have been infected with a different strain of COVID-19,’ Director of the Kirby Institute and co-author Professor Anthony Kelleher said.
 
‘What we do know is that for most people with long COVID, both their symptoms and their biomarkers improve significantly over time, and this is a cause for optimism.
 
‘Importantly, we will continue to undertake research to understand more about why some people don’t improve, and what can be done for those people.’
 
Given that full health has not been recovered two years post-SARS-CoV-2 infection for 38% of the study’s participants, the authors say further research into the pathogenesis and prognosis of long COVID is required.
 
They suggest a potential range of underlying causes for this cohort, not all of which ‘are driven by immunological abnormalities and some of which are likely to persist even when the immunological environment has largely returned to normal’.
 
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