Seroprevalence of SARS-CoV-2 antibodies among Australian blood donors following vaccine-program introduction and changes to public health and social measures


Outcomes for Australia

The focus of the 2022 national SARS-CoV-2 serosurvey program is to track the spread of COVID-19 infection in the Australian population following the high and widespread uptake of vaccination and significantly reduced public health control measures. The study will also provide estimates of population immunity based on antibody prevalence arising from a combination of vaccination (including the impact of booster doses) and exposure to infection.


Since the start of the COVID-19 pandemic, the Australian COVID-19 Serosurveillance Network has conducted four serological surveys to inform and evaluate public health responses.

Most people with SARS-CoV-2 infection generate antibodies to virus-specific antigens (nucleocapsid and spike protein antibodies) that remain detectable through blood testing for many months post-infection, even in asymptomatic cases. COVID-19 vaccination also generates an antibody response, involving the spike protein only.

Measurement of the prevalence of antibodies via serosurveys has provided a basis for estimating the cumulative proportion of the population infected at specific time points in the pandemic.

Australia is transitioning from the pre-vaccination phase of aggressive suppression to a high vaccination coverage context focussed on preventing serious COVID-19 illness, with endemic transmission anticipated nationally. In this context, we are conducting a new series of sequential cross-sectional serological surveys in 2022.


The aim of the project is to estimate SARS-CoV-2 seroprevalence in the population following either vaccination and/or natural infection and examine variations over time in relation to new variant epidemics (e.g. Omicron) and by geographic location.

The project will conduct 4 survey rounds of the blood donor population in 2022 through collaboration with our Australian Red Cross Lifeblood partners, with each survey including 5,000 samples.

Surveys commenced in March and be repeated every 13 weeks throughout 2022, estimating the seroprevalence of spike and nucleocapsid protein antibodies.

The gold standard for SARS-CoV-2 serology are neutralisation assays, which are highly specific and provide valuable information on the strength of the immune response and protection afforded. There is currently little known about the prevalence and temporal evolution of SARS-CoV-2 neutralising antibodies at a population level, and the impact of emerging variants. Of the samples collected in our study, a subset will undergo additional testing for neutralising antibodies.