[1] Ctr Dis Control & Prevent, Epidem Intelligence Serv, Atlanta, GA 30333 USA
[2] Ctr Dis Control & Prevent, Influenza Div, Natl Ctr Immunizat & Resp Dis, Atlanta, GA 30333 USA
[3] Ctr Dis Control & Prevent, Div Unintent Injury Prevent, Natl Ctr Injury Prevent & Control, Atlanta, GA 30333 USA
[4] Puerto Rico Dept Hlth, San Juan, PR USA
[5] Ctr Dis Control & Prevent, Immunizat Serv Div, Natl Ctr Immunizat & Resp Dis, Atlanta, GA 30333 USA