Months after being diagnosed with COVID-19 one in five people are still suffering from symptoms, new research finds

The rehabilitation unit at St Vincent's Public Hospital houses its Long COVID Clinic. (ABC News: Brendan Esposito)

Embargoed until: Tue 18 Jun 2024 at 0100 AEST | 0300 NZST

One in five adults infected with COVID-19 may still be suffering its effects months after their diagnosis, according to new research out of the United States.

An investigation by more than two dozen researchers found while the average time of recovery was 20 days, an estimated 22.5 per cent failed to recover 90 days after infection.

The report, based out of the United States and published in the Journal of the American Medical Association, mirrored recent reporting by Australian researchers.

The peer-reviewed study used data from the Collaborative Cohort of Cohorts for COVID-19 Research (C4R), a long-term collaboration of 14 different studies across the US.

Some of the studies have been following its own participants for up to 50 years, meaning they can now compare their health pre- and post-COVID-19 diagnosis.

A total of 4,708 participants were asked whether they were "completely recovered from COVID-19".

Once they confirmed their recovery, they were asked how long it had taken.

"[We] found that one in five adults infected with SARS-CoV-2 did not fully recover by three months post-infection in a racially and ethnically diverse US population-based sample," the report said.

"Recovery by 90 days was less likely in women and participants with pre-pandemic clinical cardiovascular disease.

"Vaccination prior to infection and infection during the Omicron variant wave were associated with greater recovery … results were similar for reinfections."

The research team noted the results may have been limited by the self-reported recovery time and the "potential for measurement error, uncontrolled confounding and selection bias".

Dr Mulu Abraha Woldegiorgis, a researcher at the Australian National University (ANU), told the ABC it was "interesting" to see the findings classified by "before and after Omicron".

"The prevalence [of long COVID] during Omicron was the same as ours," she said.

"They use slightly different definitions and methodology, but even with that the prevalence was high. It shows us that long COVID is still a public health concern globally."

Long COVID 'not just cough, or tiredness' 

Four years after the beginning of the pandemic, much about "long COVID" remains a mystery for health officials.

Earlier this year Queensland's chief health officer called for the term  "long COVID" to be scrapped despite stating the symptoms were "real".

"Using this term long COVID implies this virus has some unique, exceptional and sinister property that differentiates it form other viruses," Dr John Gerrard said.

"I want to make it clear that the symptoms that some patients describe after having COVID-19 are real. We believe they are real."

A study of more than 11,000 Australians who had tested positive for COVID-19 has had similar results — almost one in five were still experiencing symptoms three months after a 2022 diagnosis.

The ANU study, released in March, found 90 per cent of participants with long COVID were suffering multiple symptoms.

Tiredness, fatigue, "brain fog", sleep problems, coughing, and changes in their menstrual cycle were frequently reported.

"Among respondents with long COVID who had worked or studied prior to their infection, 15.2 per cent had reduced their number of hours, and 2.7 per cent had not returned to work at all," the report said.

The researchers also noted long COVID was more prevalent in its sample than the levels reported by other studies in the United Kingdom and Canada.

Dr Woldegiorgis was the lead researcher on the ANU report. She said Australia presented a "unique" cohort of highly vaccinated people.

"You have multiple symptoms, it's not just cough, or tiredness, they have multiple symptoms and that affects them," she said.

"A longer term assessment is important. What we saw was by 90 days, so a long term follow-up may provide additional information on how people are going in a year or two.

"What's the recovery period? Are they recovering soon or is the term longer?"

The report also found those who had been vaccinated were less at risk of developing long COVID.

"I want to stress the importance of vaccination," Dr Woldegiorgis said.

"In Australia the vast majority were vaccinated ... at least one dose prevents long COVID compared to no vaccination."