A Doherty Institute study found memory "T cells" that recognise long-COVID can be established and fight subsequent infections for two years.
T cells fight viral infections by killing off infected cells and can remember what they have encountered.
The study, which targeted the previously under researched area of long-COVID immunity, found specific T cells within the 31 people examined could maintain their key features over the two-year period.
Long-COVID is a chronic condition where people who have caught COVID-19 experience symptoms for an extended period of time.
It can affect almost every part of the body through extreme fatigue, muscle pain, reduced appetite, sleep problems and a host of other issues.
Doherty Institute senior research fellow Louise Rowntree said the study was good news for long-COVID sufferers, as it showed their T cells were doing what they are meant to.
"It's really positive news for someone with long-COVID … the T cells are establishing and they're maintaining," she told AAP.
"The establishment and maintenance of these cells for this two-year period really provides that protection against a subsequent infection and their responses are really good following their first vaccination as well."
The research could help shape future therapies and vaccines for long-COVID patients.
"SARS-CoV-2 vaccines stimulate both antibodies and T cell responses, so we followed the T cell responses through and it's definitely encouraging that we do need to be looking at therapies and vaccines that are going to trigger both antibodies and T cells," Dr Rowntree said.
"Those T cells can help protect when the virus mutates, so they can offer protection despite the virus changing over time."
In June, the federal government invested $14.5 million into long-COVID research to generate better evidence on effective management of the condition within the community.
The money was to be used investigating how people experience long COVID, impacts on health systems, causes and national trials to try to fast-track therapies.
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