Persistence of bactericidal antibodies to 5 years of age after immunization with serogroup B meningococcal vaccines at 6, 8, 12 and 40 months of age. by McQuaid, F, Snape, MD, John, T, Kelly, S, Robinson, H, Houlden, J, Voysey, M, Toneatto, D, Kitte, C, Dull, P, Pollard, A