[1] Natl Univ Singapore, Saw Swee Hock Sch Publ Hlth, 12 Sci Dr 2,10-01, Singapore 117549, Singapore
[2] Mongolian Natl Univ Med Sci, S Zorig St 3,POB 48-111, Ulaanbaatar 14210, Mongolia
[3] WHO, Expanded Programme Immunizat, Reg Off Western Pacific, United Nations Ave,Corner Taft Ave, Manila 1000, Philippines
[4] Minist Hlth & Sports, Govt Bldg 8,Olymp St 2, Sukhbaatar Dist 14210, Ulaanbaatar, Mongolia
[5] Royal Childrens Hosp, Murdoch Childrens Res Inst, Pneumococcal Grp, Flemington Rd, Parkville, Vic 3052, Australia
[6] Royal Childrens Hosp, Murdoch Childrens Res Inst, Int Child Hlth Res Grp, Flemington Rd, Parkville, Vic 3052, Australia
[7] Univ Melbourne, Royal Childrens Hosp, Dept Paediat, Flemington Rd, Parkville, Vic, Australia
[8] Publ Hlth England, Modelling & Econ Unit, 61 Colindale Ave, London NW9 5EQ, England
[9] London Sch Hyg & Trop Med, Dept Infect Dis Epidemiol, Keppel St, London WC1E 7HT, England
[10] Ctr Dis Control & Prevent CDC, Ctr Global Hlth, Global Immunizat Div, 1600 Clifton Rd NE, Atlanta, GA 30329 USA