Covid has hit eight in 10 of us

At least two thirds of all adults and children have contracted Covid-19, according to blood tests, but the true figure is likely to be more than eight in 10.

The SARS-CoV-2 virus. Picture: AFP

At least two thirds of all adults and children have contracted Covid-19, according to tests on the blood of thousands of Australians, but the true figure is likely to be more than eight in 10 people.

The Australian Covid-19 ­Serosurveillance Network has released its latest data based on specimens collected from 5000 blood donors, and has for the first time analysed blood samples from children to ascertain the level of Covid spread in the younger age groups.

The 2000 children’s blood samples were collected via paediatric hospitals by consent when kids were undergoing an anaesthetic procedure.

The results of the two studies showed that by September, at least two thirds of the population had been infected with SARS-CoV-2, with at least 20 per cent infected between June and the end of August.

The children and adolescents survey found at least 64 per cent of 0–19 year olds in Australia had been infected with SARS-CoV-2. In unvaccinated children aged one to four years, approximately eight out of 10 had evidence of past infection.

The network comprises scientists from the UNSW Kirby Institute, the National Centre for Immunisation Research and Surveillance, the Victorian Infectious Diseases Reference Laboratory, NSW Health Pathology’s Institute of Clinical Pathology and Medical Research and the Murdoch Children’s Research Institute, as well as co-­operation from Australian Red Cross Lifeblood. The child and adolescent study was led by the Paediatric Active Enhanced Diseases Surveillance network.

The researchers says the true cumulative prevalence of SARS-CoV-2 infection in the population is likely to be higher than indicated by their seroprevalance studies, which may miss up to 15-20 per cent of infections.

Two types of antibodies were tested in the seroprevalance studies: antibody to the nucleocapsid protein of the virus, which indicates past infection, and antibody to the spike protein, which can indicate past infection and/or vaccination.

Infectious diseases specialist at the NCIRS, Archana Koirala, said it was not a surprise to researchers that such a large proportion of the population has now had Covid-19.

“We knew that there was a wave with BA.5, and it was a kind of a different landscape where everything was open, and there was a lot of social mobility,” Dr Koirala said. “And so it’s definitely not unexpected that we saw that increase in infection and in antibody positivity.”

Dr Koirala said the children’s data in particular suggested that many more people than 65 per cent of the population had been infected.