The incidence rates of acquisition and loss of serogroup A meningococci is being investigated in the household contacts of meningococcal carriers detected during the initial cross-sectional surveys. .
Once a carrier was detected (with priority given to serogroup A carriers), all household contacts (usually in the range of 5-10) were invited to participate, swabbed fortnightly for two months, and then monthly for a further four months. This study will allow rates of acquisition and loss of carriage to be determined. A blood sample was collected at the time that the initial swabs were collected for measurement of meningococcal antibodies. These measurements will allow the titre of bactericidal antibody that provides protection against meningococcal carriage to be determined.