Meningococcal group C conjugate vaccines

Abstract

Every paediatrician knows the severity of invasive meningococcal disease and the speed at which previously healthy children can become prostrate. Five major serogroups (A, B, C, Y, and W135) are responsible for the majority of disease, the serogroup being determined by the nature of the capsular polysaccharide. The prevalence of different serogroups varies in different regions and in different age groups. Globally the greatest burden of disease comes from serogroup A which is responsible for massive epidemics in the “meningitis belt” of sub-Saharan Africa and an endemic rate which is more than 10 times that in industrialised countries.2 In much of Western Europe including the UK, more than 90% of disease is caused by serogroups B and C. Serogroup C accounts for 25–40% of cases, with the relative proportion varying in a cyclical manner from year to year. In 1995, there were 1890 reported cases of invasive meningococcal disease, an increase of 43% on the previous year.3 The majority of the increase was caused by serogroup C. Numbers of reported cases continued to rise in subsequent years, reaching a 50 year high in 1997 of 2659.4 The rise in numbers may be partly a result of better case ascertainment, but it has also coincided with the emergence of a new serogroup C clone named “ET-37” which has been responsible for a number of outbreaks of disease in many countries around the world.5-12 Many of these have attracted intense media attention. By far the majority of people with invasive disease are healthy individuals under the age of 20 with no apparent risk factors for disease. The peak incidence of disease is in infants under 1 year of age with a second peak in older teenagers.13 While 40% of disease is caused by group C in all age groups, there are more deaths attributed to serogroup C than serogroup B in the 11–24 year age group.14