The Role of Frailty in Shaping Social Contact Patterns in Belgium, 2022-2023

Social contact data are essential for understanding the spread of respiratory infectious diseases and designing effective prevention strategies. However, many studies often overlook the heterogeneity in mixing patterns among older age groups and individual frailty levels, assuming homogeneity across these sub-populations. This oversight may undermine non-pharmaceutical interventions by not targeting specific contact behaviours, potentially reducing their effectiveness in controlling disease. To address this gap, we conducted a contact survey in Flanders, Belgium (June 2022 to June 2023). Using this dataset, we reconstructed frailty-dependent contact matrices and developed a contact-based mathematical model that integrates frailty levels to investigate their impact on disease transmission dynamics. We collected data from 5,723 participants who recorded 31,375 contacts with distinct individuals. Contact patterns were observed to vary based on participants age and frailty levels, influenced by the locations of their interactions. Incorporating frailty levels into the mathematical model substantially alters the shape of epidemic curves and peak incidences. Such insights are crucial for designing tailored non-pharmaceutical interventions, indicating the need for similar data collection in different countries.