Density distribution of pharyngeal carriage of meningococcus in healthy young adults: new approaches to studying the epidemiology of colonization and vaccine indirect effects by Finn, A, Morales-Aza, B, Sikora, P, Giles, J, Lethem, R, Marlais, M, Thors, V, Pollard, A, Faust, S, Heath, P, Vipond, I, Ferreira, M, Muir, P, Januário, L, Rodrigues, F