Funding for this research was provided by:
Centers for Disease Control and Prevention (U18DP003350, U18DP003377-01)
Received: 21 December 2017
Accepted: 18 February 2019
First Online: 1 April 2019
Ethics approval and consent to participate
: All studies of this project were approved by the institutional review boards of the participating research institutes and universities in CA, MA, and TX. Written informed consent of parents and assent of children were obtained prior to data collection.
: Not applicable.
: DPO and GXA report grants from Centers for Disease Control and Prevention (CDC), during the conduct of the study. Other authors have nothing to disclose.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.