Australian COVID-19 cases higher than reported

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It is estimated that at the end of February 2022, at least 17% of the Australian adult population had recently been infected with SARS-CoV-2, the virus that causes COVID-19, according to results released today of the most recent Australian Serological Antibody Survey. virus in blood donors. The vast majority of these infections are believed to have occurred during the omicron wave which began in December 2021. According to the survey results, the proportion of people infected was at least twice as high as indicated by the cases reported to authorities in late February 2022. .

The serology survey was conducted by the National Center for Immunization Research and Surveillance (NCIRS) and the Kirby Institute at UNSW Sydney, in collaboration with Australian Red Cross Lifeblood, the Victorian Infectious Diseases Reference Laboratory and other partners of research.

The highest proportion of adults with antibodies to SARS-CoV-2 was in Queensland (26%), followed by Victoria (23%) and New South Wales (21%), while Western Australia had the lowest (0.5%).

The serological survey method detects higher proportions of infection than routine surveillance based on cases diagnosed and reported at the time of infection, which misses people who did not present for a test or whose result positive was not reported to the authorities.

The national antibody survey was conducted from late February to early March 2022, approximately 6 weeks after the peak of the omicron wave in New South Wales, the Australian Capital Territory, Queensland and Victoria and before substantial transmission in Western Australia.

“The general pattern of antibody positivity in blood donors was consistent with the pattern of reported cases up to the end of February 2022: New South Wales, Victoria and Queensland had large outbreaks and Western Australia has very limited community transmission,” explains Dr. Dorothy Machalek, principal investigator of the Kirby Institute project. “Similarly, young blood donors had the highest rate of infection, consistent with the higher number of reported cases in this age group.”

Researchers screened 5,185 anonymized samples from Australian blood donors aged 18 to 89 for evidence of antibodies linked to COVID-19. Two types of antibodies against SAR-CoV-2 have been tested: antibody against core protein, which provides an indication of past infection, and antibody against spike protein, which may indicate past infection and/or vaccination.

Evidence of past infection was highest in donors aged 18-29 at 27.2%, decreasing with age to 6.4% in donors aged 70-89 in Victoria, New -South Wales and Queensland. In Western Australia, evidence of infection was extremely low in all age groups. Nationally, the proportion of the population with antibodies to the spike protein was much higher, at around 98%.

“As expected, a very high proportion of blood donors had antibodies to the COVID-19 virus spike protein, with little variation by age group and sex. This was likely due to high vaccination rates among blood donors, as well as in the wider population,” says Professor Kristine Macartney, Director of NCIRS and Professor at the University of Sydney.

“Future rounds of blood donor serosurveys will allow us to understand how many infections are occurring throughout 2022,” Prof Macartney said. “We are also running a second national pediatric serological survey which began collection in June and this will give us better insight into transmission in children and adolescents.”

The ongoing blood donor survey, co-led by the Kirby Institute and NCIRS in collaboration with Australian Red Cross Lifeblood, also involves investigators from the Victorian Infectious Diseases Reference Laboratory at the Doherty Institute, NSW Health Pathology ICPMR, the University of Sydney and the Murdoch Children’s Research Institute.

Residual blood donation samples used in the investigation were obtained from Lifeblood processing centers across the country and disassociated of all identifying information except for age, gender and zip code. Individual results cannot therefore be returned to blood donors.

“The Australian Red Cross Lifeblood encourages anyone wishing to contribute to this type of research to become a regular donor. There are many benefits to donating, including finding out your blood type,” says Professor David Irving, Director of Research and Development at the Australian Red Cross. Vital element.

The next cycle of the Lifeblood donor survey started from mid-June. This time point will allow estimation of the prevalence of SARS-CoV-2 antibodies following the spread of Omicron BA.2 and other subvariants. Data is provided to all states, territories and the Commonwealth Government as part of Australia’s National Disease Surveillance Plan for COVID-19.

It is estimated that at least one in 500 children caught COVID-19 in the first year of the pandemic

Provided by Kirby Institute for Infection and Immunity in Society

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