Received: 6 December 2019
Accepted: 21 July 2020
First Online: 12 August 2020
Ethics approval and consent to participate
: The University of California Los Angeles and Stanford University Institutional Review Boards designated this study as “Not human subjects research” and therefore exempt from review; this was due to the study being limited to previously-existing coded data and specimens.
: Not applicable.
: The authors declare that they have no competing interests.