Summary plot showing the risk of childhood ALL associated with carriers of the DP1 supertype stratified by levels of select proxy exposure measures for early life immune modulation. ORs and 95% CIs represent the risk of childhood ALL associated with carriers of the DP1 supertype and were calculated using multivariable logistic regression adjusting for age, sex, maternal age, maternal education, annual household income, phase of study enrolled, and all other proxy measures presented. Two-way interactions between DP1 supertype carrier status and each of the 4 proxy measures separately were evaluated using a similar model, which additionally included an interaction term representing the product of the DP1 supertype and proxy exposure measure. Results for the 2 social contact variables, older sibling and daycare child-hours, were based on an analysis conducted in non-Hispanic white children only. The other 2 measures, ear infection and breastfeeding, were analyzed among all subjects because no evidence of heterogeneity was observed by race/ethnicity. Two-sided P values (P_interaction) of < .10 were considered evidence of a significantly different effect of the DP1 supertype on ALL risk between levels of the proxy exposure measure.