[1] Univ Nigeria, Teaching Hosp, Inst Child Hlth, Ituku Ozalla, Nigeria
[2] Univ Nigeria, Teaching Hosp Ituku Ozalla, Dept Paediat, Ituku Ozalla, Enugu State, Nigeria
[3] London Sch Hyg & Trop Med, WHO, Collaborating Ctr New Vaccines Surveillance, Med Res Council Unit Gambia, Banjul, Gambia
[4] Univ Lagos, Teaching Hosp, Dept Paediat, Lagos, Nigeria
[5] Univ Lagos, Coll Med, Dept Paediat, Lagos, Nigeria
[6] Univ Ilorin, Teaching Hosp, Dept Paediat & Child Hlth, Ilorin, Nigeria
[7] Abubakar Tafawa Balewa Univ, Teaching Hosp, Dept Paediat, Bauchi, Nigeria
[8] Univ Benin, Teaching Hosp, Dept Child Hlth, Cotonou, Benin
[9] WHO, Country Off, Abuja, Nigeria
[10] Natl Primary Hlth Care Dev Agcy, Dept Dis Control & Immunizat, Abuja, Nigeria
[11] Lagos Univ, Teaching Hosp, Dept Med Microbiol & Parasitol, Lagos, Nigeria
[12] Univ Nigeria, Teaching Hosp, Dept Microbiol, Ituku Ozalla, Enugu State, Nigeria
[13] Mother Christ Specialist Hosp Enugu, Enugu, Nigeria
[14] Univ Ilorin, Teaching Hosp, Dept Med Microbiol & Parasitol, Kwara, Nigeria
[15] Univ Ilorin, Teaching Hosp, Dept Epidemiol & Community Hlth, Kwara, Nigeria
[16] Abubakar Tafawa Balewa Univ, Teaching Hosp, Med Microbiol Dept, Bauchi, Nigeria
[17] Univ Benin, Teaching Hosp, Dept Med Microbiol, Cotonou, Benin
[18] Univ Benin, Teaching Hosp, Dept Community Hlth, Cotonou, Benin
[19] Lagos Univ, Teaching Hosp, Dept Community Hlth & Primary Care, Lagos, Nigeria
[20] Bernhard Nocht Inst Trop Med, Dept Infect Dis Epidemiol, Hamburg, Germany
[21] WHO, Abuja, Germany
[22] WHO, Reg Off Africa, AFRO, Brazzaville, Rep Congo
[23] Univ Warwick, Warwick Med Sch, Microbiol & Infect Unit, Coventry, W Midlands, England