Australia’s active hospital-based surveillance for severe childhood disease


The Paediatric Active Enhanced Disease Surveillance (PAEDS) Network and the National Centre for Immunisation Research and Surveillance (NCIRS) conducted a study to estimate the seroprevalence of SARS-CoV-2 antibodies in children and adolescents aged 0–19 years until August 2022, as data on notified cases of COVID-19 underestimate the true number of infections occurring in the population due to factors such as asymptomatic infections and lack of testing.

The study findings suggest there have been high rates of infection in children and adolescents of all ages across Australia, including those whose parents had not suspected infection and in vaccinated children. However, hospitalisation rates are lower, indicating children, especially those who are vaccinated, rarely experience severe disease.

Read the full paediatric serosurvey report here

Paediatric COVID-19 serosurvey: Frequently asked questions

  • What is a serosurvey?

    A serosurvey studies the number of people within a population who have antibodies against an infectious disease.

  • Which antibodies did the COVID-19 PAEDS serosurvey measure?

    The COVID-19 PAEDS serosurvey measured two types of antibodies that are produced by the human immune system against SARS-CoV-2: spike and nucleocapsid. These antibodies are produced in the body after infection or vaccination. The spike antibody lasts longer in our body while the nucleocapsid antibody wanes after a few months. In response to the COVID-19 vaccination the immune system produces spike antibodies and not nucleocapsid antibodies.

  • What did the PAEDS serosurvey find?

    The serosurvey found that at least 8 out of 10 unvaccinated children had evidence of past SARS-CoV-2 infection. All vaccinated children had spike antibodies, which is expected following vaccination, and two-thirds had nucleocapsid antibodies.

  • What are the implications of this study?

    This study helps us understand the spread of SARS-CoV-2 infection in children and adolescents. This has implications on health policy, advice around vaccination and other public health measures. It gives us a more accurate estimate of the true number of children who have been infected. These estimates show that the rate of severe infection and hospitalisation in children and adolescents is low. The presence of antibodies does not mean the person is protected against repeat infections or is experiencing long COVID.  

  • Importance of testing children

    Multiple serosurveys have tested adults, but serosurveys are hard to do in children. Blood collection can be difficult and painful. We collected blood, with consent, from children and adolescents who were already undergoing an anaesthetic at Australian hospitals. This allowed us to sample over 2,000 children in a painless manner to understand SARS-CoV-2 infection rates in this group.