Spatial clustering of low rates of COVID-19 vaccination among children and adolescents and their relationship with social determinants of health in Brazil: a nationwide population-based ecological study

OBJECTIVE: This study aimed to investigate the spatial clusters of high and low COVID-19 vaccination rates among children and adolescents across Brazilian municipalities and their relationship to social determinants of health. STUDY DESIGN: This is a nationwide population-based ecological study. METHODS: We have obtained for each of the 5570 Brazilian municipalities data on the COVID-19 vaccination rate of children and adolescents by August 16, 2022, the Gini index, the social vulnerability index and the municipal human development index. A Bayesian empirical local model was used to identify fluctuations in the COVID-19 vaccination rates. Spatial clusters were identified using scan spatial statistic tests. The relationship among COVID-19 vaccination rates and social determinants of health was explored by using multiple linear regression models. RESULTS: Overall, 52.1% of children aged 5–11 years and 72.8% of adolescents aged 12–17 years have been fully vaccinated against COVID-19 in Brazil by mid-August 2022. There was spatial dependence on the smoothed rates for both children (I Moran 0.66; P < 0.001) and adolescent (I Moran 0.65; P < 0.001) groups. The lowest rates occurred in municipalities in the North and Northeast regions. Municipalities with a higher Gini Index, higher social vulnerability index and lower municipal human development index were more likely to have a lower COVID-19 vaccination rate for both children and adolescent groups. CONCLUSION: COVID-19 vaccination of children and adolescents was heterogeneously distributed, with spatial clusters of the lowest vaccination rates occurring mainly in municipalities with marked socio-economic disparities and social vulnerability, especially in the North and Northeast regions.