A new study has looked at the causes of differing levels of COVID-19 severity. 

New research from the University of New South Wales has found hidden immune system issues may explain why some get severe COVID-19 while others are fine. 

The scientists say it may be because those who do become very unwell have undiagnosed immunodeficiencies (faulty immune systems). 

The research found genetic defects that compromise the immune system in patients with life-threatening COVID-19, and say just these particular defects may account for between 3 and 5 per cent of all severe COVID-19 cases among people under the age of 70. 

They also say immune-system-related antibodies which stop the body from fighting COVID-19 effectively were found in around 20 per cent of severe COVID-19 cases in the under 70s, and in 20 per cent of patients who died from the disease. 

The researchers conclude that therapies that target immunodeficiencies may be effective in stopping COVID-19 from becoming severe in patients with these issues.

The study is accessible here.