The investigators analysed 5339 de-identified blood samples,from patients having routine blood tests,blood donors,and women having pregnancy checks,between late April and early June,capturing infections up to mid-May.
If the results were extrapolated to Sydney's five-million-odd population,only one in 670 people had been infected during the city's first wave,according to the not yet peer-reviewed analysis.
That amounted to 7450 COVID-19 cases – more than 3.5 times the 2118 confirmed cases officially detected at the time,investigators co-led by researchers at the National Centre for Immunisation Research and Surveillance (NCIRS),UNSW's Kirby Institute and NSW Health Pathology's Institute of Clinical Pathology and Medical Research (ICPMR) reported.
Lead author Associate Professor Heather Gidding from the NCIRS said the low prevalence of antibodies detected in the study confirmed limited transmission of the virus in Sydney during the first wave.
"Compare that 7450 infections to the daily number of cases reported on a daily basis in parts of Europe and the Americas. It really is such a small number,"Associate Professor Giddings said.