1 Meningitis and Vaccine Preventable Diseases Branch, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA 30329, USA. Electronic address: vif6@cdc.gov.
2 Meningitis and Vaccine Preventable Diseases Branch, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA 30329, USA.