Long COVID in children in Australia and the potential impact of vaccination

Long COVID (LC) or Post-COVID condition (PCC) is a serious illness that can result in chronic conditions in all ages, including children. We used SARS-CoV-2 infection-induced data to find monthly seroprevalence in 6 months to 11 year olds in 2021-2022 to estimate the proportion experiencing PCC. A non-dynamic model using age-specific PCC rates, in accordance with the WHO definition of LC and the National Academies of Sciences, Engineering, and Medicine (NASEM) definition of PCC, was applied to estimate the burden of LC in children during 2021-2023 and to evaluate the impact of vaccination under different coverage and vaccine effectiveness (VE) scenarios. By the end of 2022, seroprevalence was higher among children aged 5-11 years (85.6%) than among those aged 6 months-4 years (77.9%). However, a higher proportion of the youngest age experienced LC (approximately 0.8%), compared with children aged 5-11 year (approximately 0.3%). The low vaccination coverage achieved in the 5-11 age group (40%) averted approximately 9% of infections and reduced LC prevalence by 13% at the end of 2022 under the assumption of no waning VE. If children aged 6 months-4 years age group, who were ineligible for routine vaccination, had been vaccinated at the same uptake level, infections and LC prevalence could have been reduced by approximately 5% and 10%, respectively. Achieving coverage comparable to that of adults aged 70 years and older (94%) would have resulted in substantially larger reductions in infections (∼ 32%-55%) and LC prevalence (∼34%) in both paediatric age groups. However, assuming VE waning 12% per month, the reduction in seroprevalence and LC prevalence are limited to 2-4%, depending on coverage. These findings suggest that vaccination can reduce LC burden in children, which should be considered in vaccine policy.