1. Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
2. Vaccine Preventable Disease Surveillance Unit, Minnesota Department of Health, St. Paul, MN, USA
3. Vaccine-Preventable Diseases, Washington State Department of Health, Shoreline, WA, USA
4. Comprehensive Family Immunization Unit, Pan American Health Organization, Washington, DC, USA
5. Pan American Health Organization, Lima, Perú
6. Public Health Ontario, Toronto, ON, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
7. School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, Australia