Insights into the role of children in the COVID-19 pandemic in Belgium: a longitudinal sensitivity analysis

Abstract Understanding the evolving role of different age groups in virus transmission dynamics is essential for informed pandemic management. This study delves into the age-related transmission patterns of SARS-CoV-2 in Belgium from November 2020 to February 2022. We employed a next-generation matrix approach, integrating longitudinal social contact data and numerical simulations of the evolving population susceptibility. A perturbation analysis of the effective reproduction number (Rt ) underscored the age-specific transmission patterns. From November to December 2020, adults aged [18,60) were main contributors to Rt (≈ 78%), with children aged [0,12) having a marginal role (≈ 3.7%). This pattern shifted between January and March 2021, coinciding with in-person education resumption and the Alpha variant emergence; children’s contribution to Rt increased to ≈ 38%. Stringent measures in March 2021 significantly reduced transmission levels, substantially downsizing the role of the [18,30) age group. Following the summer school break, in September-October 2021, we observed a notable resurgence in children’s contribution to Rt . Our findings highlight the noteworthy and varying influence of the [0,12) age group on SARS-CoV-2 transmission, offering insights to design nuanced pandemic responses, e.g., that balance public health needs with socio-educational implications of interventions like extended school closures. Overall, this study demonstrates the effectiveness of our methodology in uncovering age-specific transmission patterns in the study of infectious disease spread.