Many of those who had COVID-19 did not experience symptoms, making it hard to know how many people were infected with the virus during ‘waves’ of the pandemic. Researchers used a ‘back-calculation’ statistical model to examine the first and second waves in 2020 and showed that the reported cases were only half of the story – that for every known case there was an additional unknown case.

This means a truer estimate for wave 2 was 95,000 cases rather than the reported 48,390 cases. The project showed that this type of statistical analysis helps us to better understand the prevalence of an infectious disease and can inform decisions about appropriate measures to protect people.

Back-calculation to ‘see’ the invisible cases is part of a wider selection of success stories across four themes from this year’s annual Health Research in Action.

Download the full Health Research in Action publication (549 kB).

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