On multilevel logistic analysis with three nested levels ( student , school , school district ) during both vaccination seasons , children were more likely to be vaccinated in SLV-I versus control schools ; ORs were 1.6 ( 95 % CI = 1.4 , 1.9 ; p < 0.001 ) and 1.5 ( 95 % CI = 1.3 , 1.8 ; p < 0.001 ) .