In Reply We thank Drs Yew and Tey for their interest in our study.1 We are, however, concerned about their interpretation of our study results. Secondary analyses, as well as interpretations of analyses that were not part of the original study design, can result in spurious conclusions. Our study was not designed to evaluate only individuals of aged 1 to 4 years and was not designed to specifically study acute lymphoblastic leukemia (ALL). The investigation was designed to study all cancer and lymphoma in children (aged 2 to 18 years) as a group who were or will be followed for up to 10 years.