In each country, immediate processing of pharyngeal swabs will allow the identification of subjects who are carrying meningococci and the serogroup of these meningococci will be determined within 2 - 4 days of collection of the sample. The households of these subjects will be visited as soon as possible after identification of a carrier has been made, informed consent will be obtained and if the participant agrees, a pharyngeal swab will be obtained twice a month for two months and monthly for a further four months, a total of 8 follow-up samples to estimate the rates of acquisition and loss of carriage in household's contacts. During the first visit, a 5 ml blood sample will be obtained from all subjects over the age of 6 months for measurement of IgG ELISA and bactericidal serogroup A meningococcal antibodies to determine concentrations that protect against acquisition of carriage. No further blood samples will be collected. A rapid diagnostic test for malaria will be performed on any subject who is febrile or unwell and antimalarial treatment provided according to the national guidelines if it is positive. The results of these household studies will show the impact of vaccination on acquisition rates of carriage.