SARS-CoV-2 transmission across age groups in France and implications for control

Résumé 0

The shielding of older individuals has been proposed to limit COVID-19 hospitalizations while relaxing general social distancing in the absence of vaccines. Evaluating such approachesrequires a deep understanding of transmission dynamics across ages. Here, we use detailed agespecificcase and hospitalization data to model the rebound in the French epidemic in summer2020, characterize age-specific transmission dynamics and critically evaluate different agetargetedintervention measures in the absence of vaccines. We find that while the rebound startedin young adults, it reached individuals aged ≥80 y.o. after 4 weeks, despite substantial contactreductions, indicating substantial transmission flows across ages. We derive from these patternsthe contribution of each age group to transmission. While shielding older individuals reducesmortality, it is insufficient to allow major relaxations of social distancing. When the epidemicremains manageable (R close to 1), targeting those that contribute more to transmission is betterthan shielding at-risk individuals. Pandemic control requires an effort from all age groups.