[1] Withington Hosp, PHLS Meningococcal Reference Unit, Manchester M20 2LR, Lancs, England
[2] PHLS Communicable Dis Surveillance Ctr, Immunisat Div, London, England
[3] London Sch Hyg & Trop Med, Dept Infect & Trop Dis, London WC1, England
[4] Max Planck Inst Mol Genet, Berlin, Germany
[5] Inst Pasteur, Meningococcal Reference Ctr, Paris, France
[6] Inst Pasteur, Neisseria Unit, Paris, France