The largest study of COVID-19 recovery time ever undertaken in Australia found four in five patients recovered within a month, 1.8 per cent died and 4.8 per cent were still experiencing symptoms after three months.

The most commonly reported residual symptoms were cough and fatigue, the study found. Older people, women and those with co-morbidities had slower recovery times.

The study was published on Friday in the Lancet Regional Health - Western Pacific.

The study's lead author, University of NSW associate professor Bette Liu, said there was a good understanding of acute clinical presentations when patients were hospitalised for COVID-19 but less knowledge of those with milder symptoms.

"Our data demonstrates the substantial direct impact of COVID-19 on population health and the need to consider not only hospitalisations and deaths, but also the longer-term health of those with less severe forms of the disease," Dr Liu said in a statement.

Dr Liu said the study showed prolonged recovery from the virus would be a "significant problem" for many of the more than 30,000 confirmed cases in Australia to date.

Although younger people recovered more quickly, Dr Liu said two per cent of people aged under 30 still had symptoms after three months.

The study interviewed and tracked 94 per cent of people diagnosed with COVID-19 in NSW between January and May 2020. Researchers said this access made their estimates more reliable than previous smaller studies which had been restricted to volunteers or those hospitalised with the virus.

"This study demonstrates how important it is that we all protect ourselves from COVID-19 through following public health advice, including hand hygiene, physical distancing and testing, as well as getting vaccinated when it is your turn," Dr Liu said.

Australian Associated Press