Epidemiology

The incidence of bacterial meningitis in Europe and the US is estimated at 0.7 to 0.9 in 100,000 people per year and has decreased by 3% to 4% in the past 10 to 20 years.[5]

The incidence in African countries is 10 to 40 in 100,000 people per year, reflecting the high rates of disease seen in epidemics of meningococcal meningitis occurring throughout the African meningitis belt during the dry season.[5][6][7] Globally, of the top 10 countries with the greatest absolute number of meningitis deaths, four are located outside the African meningitis belt (India, Pakistan, Afghanistan, China).[8]

The epidemiology of bacterial meningitis has changed due to widespread immunization programs, including the introduction of protein-polysaccharide conjugate vaccines. In countries with universal Haemophilus influenzae type b (Hib) immunization programs, the incidence of Hib meningitis has declined by 95% to 99%.[5][9]

Pneumococcal meningitis

In the US, where the heptavalent pneumococcal vaccine was introduced in 2000, the overall rates of pneumococcal meningitis have declined significantly from 0.8 in 100,000 in 1997 to 0.3 in 100,000 in 2010. A further decline in pneumococcal meningitis, particularly in patients ages 2 years or less, was recorded subsequent to the introduction of the 10- and 13-valent vaccines in 2010.[10][11][12]

Meningococcal meningitis

Most outbreaks of Neisseria meningitidis meningitis outside Africa are caused by meningococcal serogroups B and C, with emergence of serogroup W135 since 2012.[7] In Africa, serogroups A, C, and W account for substantial proportions of meningococcal disease.[13] Meningococcal vaccines are available for serogroups A, B, C, W, and Y.

In the US, the incidence of meningococcal meningitis decreased from 0.72 in 100,000 in 1997 to 0.12 in 100,000 in 2010.[10] This decrease has been linked to the introduction of the quadrivalent meningococcal conjugate vaccine in 2005. A decrease in incidence was also witnessed in other countries with conjugated vaccine uptake. In the UK, serogroup C vaccination was implemented in 1998 and serogroup B vaccination in 2015.[14] Much of the beneficial effect of these vaccines was achieved by herd immunity.[15]

[Figure caption and citation for the preceding image starts]: Laboratory-confirmed cases of invasive meningococcal disease in England by capsular group and epidemiologic year. The light blue and dark blue arrows denote the start of the national immunization programme against group C meningococcal (MenC) disease and group B meningococcal (MenB) disease, respectivelyPublic Health England [Citation ends].com.bmj.content.model.Caption@3fc9494f

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