1 Department of Pediatrics, University of California at Los Angeles, Los Angeles, CA 90095, USA. Electronic address: pszilagyi@mednet.ucla.edu.
2 Department of Pediatrics, Division of Urgent Care, Children's Mercy Kansas City, UMKC School of Medicine, Kansas City, MO 64106, USA. Electronic address: sharon@immunize.org.
3 Division of Adolescent Medicine, Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL 35233, USA. Electronic address: tcoynebeasley@uabmc.edu.