Two studies looked at blood samples, known as serology, in children and adolescents, with the other focusing on adults. The survey of children and adolescents found that at least 64 percent of people aged 19 and under had antibodies that suggested they had been infected with the virus. Kobie, aged 11, has blood tests at The Children’s Hospital in Westmead. (Is provided) In unvaccinated children aged one to four, about eight in 10 had evidence of previous infection. The study of children and adolescents was conducted by the Pediatric Active Disease Surveillance Network (PAEDS) and the National Center for Immunization Research and Surveillance (NCIRS), in collaboration with the Infectious Disease Reporting Laboratory of Victoria. A total of 2,046 blood samples were tested, which were collected between June and August this year. Dr. Archana Koirala, an infectious disease specialist at NCIRS and the lead of the pediatric study, said the findings are more than double the number of cases reported based on the nose and throat test for the virus. COVID-19 is seen under a microscope. (Getty Images/iStockphoto) “Overall, this study tells us that at least two-thirds of children in Australia have had COVID-19,” he said. “This is to be expected as many children have mild or no symptoms and therefore are not tested for the virus. Looking at both vaccination status and infection history in our study, we found that four out of 10 children with no reported history of COVID-19 actually tested positive for antibodies, indicating infection. Antibodies decline over time, meaning the true number of COVID-19 infections in children could be much higher. These file images show pneumonia in the lungs of a coronavirus patient. (New England Journal of Medicine) Koirala said the serology findings underscore the importance of vaccinations. “Vaccination reduces the risk of severe disease if infected with the virus and should continue to be taken according to current national recommendations that have been updated by these data,” he said. The adult serosurvey, led by NCIRS with the Kirby Institute and the Australian Red Cross, found that at least 65 percent of adults had antibodies indicating a previous infection with COVID-19, a similar rate to the children studied. That was an increase of about 20 percent from a study three months earlier, with researchers believing these people had been exposed to the virus in the intervening months. The highest prevalence was in the 18-29 age group, with 80 percent indicating previous infection with COVID-19. This drops to 42 percent in 70-year-olds The adult survey was conducted by analyzing residual blood donations at three-month intervals, with infection rates similar across states and territories. The subvariants and mutations of COVID-19
