Epidemiological Data

The majority of meningococcal disease occurs in infants less than five years of age, with a peak incidence in those under 1 year of age. There is a smaller, secondary peak in incidence in young adults aged between 15 - 19 years of age.

Most cases of meningococcal disease occur sporadically, with less than 5% of cases occurring in clusters. Outbreaks of meningococcal disease are more common among teenagers and young adults, and outbreaks have been reported in schools and universities. Public health interventions may include vaccination (depending on serogroup) and chemoprophylaxis.

Meningococcal disease shows marked seasonal variation with a peak in winter and a low level in summer. The winter season coincides with that of influenza. (see News and Events, Seasonal Diseases) Laboratory Confirmed Cases of Meningococcal Disease England & Wales Five Weekly Moving Averages: 1999 to 2009.

Meningococci are divided into distinct serogroups, according to their polysaccharide outer capsule. The most common serogroups that cause disease worldwide are groups B, C, A, Y and W135. Prior to the introduction of Men C vaccine, most disease in the UK was caused by serogroups B and C. Between 1996 - 2000 serogroup B accounted for 59% of all cases, group C (36%) and other groups including W135 & A (5%).

However, the number of cases caused by serogroup C have significantly reduced in all age groups since routine Men C vaccination was introduced (see Vaccination against Meningococcal disease) and serogroup B now accounts for 85-90% of all cases of meningococcal disease.

Meningococcal disease has an overall case fatality rate of approximately 10%, however this varies by a number of factors, including serogroup, age, and prompt antibiotic treatment. More deaths are caused by septicaemia than by meningitis.

Epidemiological data is obtained from 3 main sources:

Notifications: Based on clinical diagnosis (statutory)
Laboratory Confirmed Reports of invasive meningococcal disease: Routine laboratory reports using data from the Meningococcal Reference Unit (MRU)
Death data: From Office of National Statistics' death certificate information. Data from the routine laboratory reporting system (from the MRU) and ONS deaths are matched.