Australian researchers believe COVID-19 vaccines will work for longer periods, after testing the immunity of people who had contracted the disease.

Australian researchers have discovered that patients who've been infected with COVID-19 retain immunity against the virus and the disease for at least eight months.

The research is the strongest evidence yet that vaccines against the virus will work for long periods.

Previous studies found the first wave of antibodies produced by the human body after infection waned after the first few months, raising concerns that people could quickly lose immunity.

The new research allays those concerns.

The study is the result of a collaboration led by Associate Professor Menno van Zelm, from Monash University and was published on Monday in the preprint server, MedRxiv.

The researchers found a specific cell within the human immune system, the memory B cell, "remembers" infection by the virus, and if challenged again, through re-exposure to the virus, triggers a protective immune response through rapid production of protective antibodies.

The researchers recruited 25 COVID-19 patients and took 36 blood samples between day four post-infection and day 242 post-infection.

As with other studies, looking at the antibody response, the researchers found that antibodies against the virus started to drop off after 20 days post-infection.

However, all patients continued to have memory B cells that recognised one of two components of the virus, the spike and nucleocapsid proteins.

These virus-specific memory B cells were present as long as eight months after infection.

Associate Professor van Zelm said the results gave hope to the efficacy of any vaccine against the virus and explained why there had been so few examples of genuine reinfection in the millions of people who had tested positive for the virus globally.

"These results are important because they show, definitively, that patients infected with the COVID-19 virus do in fact retain immunity against the virus and the disease," he said.

"This has been a black cloud hanging over the potential protection that could be provided by any COVID-19 vaccine and gives real hope that, once a vaccine or vaccines are developed, they will provide long-term protection."