In February Omicron cases were at an all time high.
More than one and a half million people had been been infected, as millions more queued for testing.
But a recent survey of blood donors found the real rate of infection to be much larger than records reveal.
Professor John Kaldor from the Kirby Institute says the real figure was likely double what had originally been recorded.
The survey examined 5,000 samples from blood donors - looking for antibodies specific to infection - not vaccination.
It found, by the end of February, at least 17 per cent of the population had recently been infected, among younger age groups that figure rose to 27 per cent.
The highest proportion of antibodies were found in Queensland, followed by Victoria and New South Wales, whilst the lowest levels were in W-A.
Meanwhile, another team of researchers at Queensland Health and Q-I-M-R Berghofer are trying to determine why people have widely varying immune responses to the Covid-19 vaccine and the virus itself.
People who've had a vaccine or booster within the past three months are being asked to sign up for the QoVaX study.
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