The natural history of meningococcal carriage and disease

Abstract

The prevalence of Neisseria meningitidis carriage is highest in teenagers and lowest in young children. In contrast, invasive meningococcal disease is most common in young children with a smaller secondary peak in teenagers. Data on carriage and disease were analysed to quantify the risks of infection and disease by age and serogroup. The forces of infection for serogroups B, C, other meningococci and Neisseria lactamica were modelled together with the risk of disease given infection for serogroups B and C, using maximum likelihood to fit the models to the available data. The risk of meningococcal disease given infection declines steeply through childhood and is higher for serogroup C than for serogroup B. The secondary peak in disease in teenagers appears to be explained mostly by increased transmission although there is a suggestion that other factors may also contribute. These analyses provide important insights and may be used to guide further data collection and modelling studies.

Fig. 1

Comparison of age-specific prevalence of (a) N. meningitidis and (b) N. lactamica carriage in Stonehouse (▪) and Danbury (▴). The upper and lower 95% confidence intervals are shown.

Fig. 2

Estimated average cumulative episodes of carriage by age.

Fig. 3

Risk of disease given infection by age and serogroup (a) using disease incidence data from the late 1980s/early 1990s (Table 1) and the Stonehouse/Danbury carriage dataset. (b) Using disease incidence data from the late 1990s (Table 1) and the Stonehouse/Danbury carriage dataset.

Fig. 4

Comparison of the risk of disease given infection and the proportion of individuals not previously infected.

Fig. 5

Carriage prevalence estimated by SIS model (best-fit force of infection parameters) compared to observed data (see Appendix 1 for more details on the functions and parameters used).