[1] US Ctr Dis Control & Prevent, Div Viral Hepatitis, Atlanta, GA 30333 USA
[2] US Ctr Dis Control & Prevent, Div Hlth Care Qual Promot, Atlanta, GA 30333 USA
[3] US Ctr Dis Control & Prevent, Div Bacterial & Mycot Dis, Natl Ctr Infect Dis, Atlanta, GA 30333 USA
[4] US Ctr Dis Control & Prevent, Epidemiol & Surveillance Div, Natl Immunizat Program, Atlanta, GA 30333 USA