Background and Objective:
Children and adolescents are highly vulnerable to the impact of sustained stressors during developmentally sensitive times. Therefore, long-term adverse effects of the pandemic warrant special consideration. However, children are not a homogeneous group: the intersection of social, economic, and demographic characteristics shapes childrens daily experiences and outcomes. We investigated how demographic characteristics intersect with socioeconomic dimensions to shape the social patterning of quality of life and mental health in children and adolescents, two years into the COVID-19 pandemic.

Methods:
We used data from the prospective SEROCoV-KIDS cohort study of children and adolescents living in Geneva (Switzerland). We conducted an intersectional Multilevel Analysis of Individual Heterogeneity and Discriminatory Accuracy (MAIHDA) by nesting participants within 48 social strata defined by intersecting sex, age, migrant status, parental education and financial hardship in Bayesian multilevel logistic models for poor health-related quality of life (HRQoL, measured with PedsQL), and poor mental health (SDQ).

Results:
Among participants aged 2-17 years (median 10, IQR7-13), 223/1954 (11.4%) and 100/1991 (5.0%) had poor HRQoL and poor mental health, respectively. We observed substantial between-stratum differences in the predicted proportion of poor HRQoL, ranging from 4.4% for 2-5 years old Swiss-born females with highly educated parents and no financial hardship to 33.3% for 12-17 years old Swiss-born females with highly educated parents but financial hardship. Strata including adolescents and financial hardship had a significantly higher likelihood of poor HRQoL than their counterparts. Between-stratum variations in the predicted frequency of poor mental health were limited (range 4.2%-6.8%) and mainly explained by low parental education.

Conclusion:
We found evidence of considerable differences in adverse outcomes across social strata. Interventions to address inequities in HRQoL should focus on specific population sub-groups involving adolescents and families with financial hardship, while those aiming to improve mental health should target all children and adolescents.