Most children with COVID-19 last year had mild cases, didn't require medical care and made a full recovery within weeks of infection, according to new research.

Two studies led by the Murdoch Children's Research Institute (MCRI) in 2020 found children with COVID-19 experienced milder symptoms and less severe health complications compared to adults.

Research, published in The Lancet Child & Adolescent Health journal, found of the 171 children aged under 18 years who tested positive for SARS-CoV-2 in Victoria in the seven months to October 28, 2020, 58 percent had mild disease, 36 percent were asymptomatic and 5 percent had moderate disease.

MCRI Dr. Shidan Tosif said all children recovered well and the common long-term symptoms of a cough and fatigue did not persist beyond eight weeks.

"Unlike adults who can experience ongoing and serious health issues such as fatigue and lung problems, even with a mild case COVID-19, we are yet to see any long-term effects beyond two months in these children," he said.

MCRI Dr. Laila Ibrahim said her study, published in The Medical Journal of Australia, which involved 16 hospitals across Australia, found children were less likely to be affected by COVID-19 in comparison with adults.

The data, tracked through the Pediatric Research in Emergency Departments International Collaborative (PREDICT) network, involved children who tested positive for SARS-CoV-2, in the seven months to September 30, 2020. Of 426 hospital presentations, 393 children tested positive for COVID-19 and most had mild cases that did not require medical intervention. Only one child had severe COVID-19 and another two children developed Pediatric Inflammatory Multisystem Syndrome, temporally associated with SARS-CoV-2 (PIMS-TS).

The study found just 12% were admitted to the hospital with 4% treated at home remotely by a Hospital-in-the-Home program.

"Hospital admissions were generally brief, for observation or fluid rehydration," Dr. Ibrahim said. "On average, children tested positive after two days of having symptoms such as fever, runny nose and a cough and many had household contacts who were also positive for COVID-19."

MCRI Professor Franz Babl said grouping patients in emergency departments into "high risk" and "low risk" categories based on symptoms may provide false reassurance.

"Our study showed that occasionally children with COVID-19 will be missed in the emergency department as some infants only had lethargy as a symptom," he said.

"There is also a high proportion of repeat presentations to the hospital. Ambulatory monitoring or the Hospital-in-the-Home program may reduce re-attendance to emergency departments and transmission risks."