Seasonal patterns of SARS-CoV-2 transmission in secondary schools: a modelling study

BackgroundThe Omicron variant has caused a new wave of SARS-CoV-2 infections worldwide. We explore crucial epidemiological parameters driving seasonal patterns of SARS-CoV-2 transmission in secondary schools and assess various infection control interventions over a 2.5-year time frame. MethodsWe developed an agent-based model parameterised with data from secondary schools in the Netherlands. We modelled the circulation of Omicron assuming a stable introduction rate of infections and accounted for uncertainty in epidemiological parameters describing virus transmissibility, susceptibility to reinfection, vaccine immune escape, and waning of sterilising immunity. We quantified the SARS-CoV-2 health burden defined as number of symptomatic student days. We further evaluated the cost-benefit (number of prevented infected students per absent student) for reactive quarantine interventions, regular screening using antigen tests, and annual booster vaccinations. FindingsDurability of sterilising immunity is a key parameter that governs temporal SARS-CoV-2 transmission patterns in secondary schools. Our model predicts pronounced within-school seasonal patterns with dominant autumn outbreaks and smaller winter outbreaks and a maximum prevalence of 2.9% (95% CI: 0.7%-6.6%) symptomatic students during infection peaks. Regular screening and annual booster vaccination may reduce the health burden up to 15% (95% CI: 1.5%-27.8%) and have a higher cost-benefit ratio than reactive quarantine interventions (reduction: 4.3%; 95% CI: -10.1% to 17.6%). InterpretationImmunity waning will determine the intensity and pattern of SARS-CoV-2 transmission in secondary schools in the medium-term future. If mitigation strategies are needed, screening and annual booster vaccination have the highest cost-benefit by reducing viral transmission with little educational disruption.