Vaccine Preventable Diseases in Australia, 2005 to 2007

3.7 Meningococcal disease

Page last updated: 24 December 2010

Meningococcal disease is defined for surveillance purposes as the isolation of the bacterium Neisseria meningitidis from cerebrospinal fluid, blood and other normally sterile sites including skin lesions. Clinical manifestations include meningitis, meningococcaemia without meningitis (which varies in presentation from fulminant to chronic), a mixture of meningitis and septicaemia, and septic arthritis. In culture-negative cases with a compatible clinical picture (such as fever, haemorrhagic rash and shock), a diagnosis of meningococcal disease can be supported by a range of laboratory evidence. This includes the identification of Gram-negative intracellular diplococci or meningococcal antigen in, for example, blood or cerebrospinal fluid; the identification of nucleic acid from N. meningitidis in body fluids; or demonstration of a serological response to N. meningitidis.1,2

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Case definitions

Notifications

See Appendix 6.6 for pre-2004 definition

National definition from January 2004:*3

Both confirmed and probable cases are notifiable. Confirmed cases require either laboratory definitive evidence, or laboratory suggestive evidence together with clinical evidence. Probable cases require specified clinical evidence only (as below).

  1. Laboratory definitive evidence
    • Isolation of Neisseria meningitidis from a normally sterile site.
  2. Laboratory suggestive evidence
    • Detection of meningococcus from a normally sterile site by nucleic acid testing; or
    • Detection of Gram-negative diplococci in Gram stain of specimen from a normally sterile site or from a suspicious skin lesion; or
    • High titre IgM or significant rise in IgM or IgG titres to outer membrane protein antigens of N. meningitidis; or
    • Positive polysaccharide antigen test in cerebrospinal fluid with other laboratory parameters consistent with meningitis.
  3. Clinical evidence (for notification of confirmed cases, together with laboratory suggestive evidence)
    • Disease which in the opinion of the treating clinician is compatible with invasive meningococcal disease.
  4. Clinical evidence for notification of probable cases
    • The absence of evidence for other causes of clinical symptoms and either
    • Clinically compatible disease including haemorrhagic rash; or
    • Clinically compatible disease AND close contact with a confirmed case within the previous 60 days.

* The national case definition was revised and endorsed by CDNA in October 2007. Time of implementation of the revised case definition varied among different jurisdictions following the revision.

† ‘Detection of meningococcus from a normally sterile site by nucleic acid testing’ is considered laboratory definitive evidence in the revised case definition of October 2007.

‡ ‘Positive polysaccharide antigen test in cerebrospinal fluid with other laboratory parameters consistent with meningitis’ is no longer accepted as laboratory suggestive evidence in the revised case definition of October 2007.

Hospitalisations

The ICD-10-AM code used to identify hospitalisations was A39 (meningococcal infection). This includes meningococcal meningitis (A39.0), Waterhouse-Friderichsen syndrome (A39.1), acute meningococcaemia (A39.2), chronic meningococcaemia (A39.3), meningococcaemia unspecified (A39.4), meningococcal heart disease (A39.5), other meningococcal infections (A39.8), and meningococcal infection unspecified (A39.9). As all cases with one of these codes, not just principal diagnoses, were included, cases were identified in a hierarchical fashion to avoid double counting. First, those with code A39.0 (meningitis), then those without A39.0 but with A39.1 or A39.2 or A39.3 or A39.4 (septicaemia without meningitis), then those with none of these codes but with codes in any other subsection of A39 were selected. However, as re-admissions and inter-hospital transfers are separate records, duplication may occur for a condition such as meningococcal disease where complications are frequent.

Deaths

The ICD-10 code used to identify deaths recorded in the AIHW National Mortality Database was A39 (meningococcal infection).

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Secular trends

There were 622 notifications of meningococcal disease in the 2 years 2006–2007, an average annual notification rate of 1.5 per 100,000 population (Table 3.7.1). A median of 24.5 cases was notified each month, with a range of 8–49 cases. Between July 2005 and June 2007, there were 1,024 episodes of hospitalisation recorded as ICD-10-AM code A39 (average annual rate 2.5 per 100,000), and a median of 38 admissions (range 9–73) per month. Coinciding with the introduction of the national meningococcal C immunisation program in January 2003,4 both the notification and hospitalisation rates for meningococcal disease decreased each year, down from a peak in 2002 (Figure 3.7.1). The notification rate for meningococcal disease of any serotype decreased by 57% from 3.5 cases per 100,000 in 2002 to 1.5 cases per 100,000 in 2007 (Appendix 6.2), while the hospitalisation rate for all meningococcal disease decreased by 53% from 4.5 per 100,000 in 2002/2003 to 2.1 per 100,000 in 2006/2007 (Appendix 6.3).

Figure 3.7.1: Meningococcal notifications and hospitalisations, Australia, 1993 to 2007,* by month of diagnosis or admission

Figure 3.7.1:  Meningococcal notifications and hospitalisations, Australia, 1993 to 2007, by month of diagnosis or admission

* Notifications where the date of diagnosis was between January 1993 and December 2007; hospitalisations where the date of admission was between July 1993 and June 2007.

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A clear seasonal pattern was apparent, with the highest number of notifications and hospitalisations occurring between June and September each year (Figure 3.7.1).

Table 3.7.1: Meningococcal notifications, hospitalisations and deaths, Australia, 2005 to 2007,* by age group

Age group
(years)
Notifications
2 years
(2006–2007)
Hospitalisations
2 years
(July 2005–June 2007)
LOS per admission
(days)
Deaths
2 years
(2005–2006)
n Rate n (§) Rate (§) Median (§) n Rate
0–4
222
8.4
381
(359)
14.7
(13.8)
4.0
(4.0)
15
0.58
5–14
63
1.1
141
(133)
2.6
(2.4)
2.0
(3.0)
2
0.04
15–24
180
3.1
242
(213)
4.2
(3.7)
5.0
(5.0)
3
0.05
25–59
116
0.6
182
(151)
0.9
(0.8)
7.0
(6.0)
7
0.03
60+
41
0.5
78
(48)
1.1
(0.7)
11.0
(8.0)
5
0.07
All ages
622
1.5
1,024
(904)
2.5
(2.2)
5.0
(5.0)
32
0.08

* Notifications where the date of diagnosis was between January 2006 and December 2007; hospitalisations where the date of separation was between July 2005 and June 2007; deaths where the death was recorded between January 2005 and December 2006 on the AIHW National Mortality Database.

† LOS = length of stay in hospital.

‡ Average annual age-specific rate per 100,000 population.

§ Principal diagnosis (hospitalisations).

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Severe morbidity and mortality

A total of 7,482 hospital bed days (average 3,741 days per year) were recorded for patients with an ICD-10-AM code of A39, of which 48% were coded as meningococcal meningitis (A39.0) and 36% were coded as septicaemia (A39.1–A39.4, not A39.0). The proportion of hospitalisations where a meningococcal disease code was the principal diagnosis varied from 94% of cases among the 0–14 year age group to 86% of cases for those aged 15–59 years and 62% for those aged ≥60 years. The median length of hospital stay was 5 days and increased with age (Table 3.7.1).

Information about deaths was available from three different sources for overlapping time periods. All show an overall downward trend.

Death certificate data: In 2005 and 2006 there were 32 deaths (0.08 per 100,000 population) with meningococcal disease recorded as the underlying cause of death (Table 3.7.1). Twenty-five (78%) were coded as septicaemia (A39.1–A39.4, not A39.0).

Hospitalisation data: Of the 1,024 hospital separations during the period July 2005–June 2007, 24 (2.3%) were recorded as dying in hospital. The proportion of meningococcal infection hospitalisations with death as the outcome was lowest in the 5–24 year age group (1%) and highest in those aged ≥60 years (6%). Case fatality rates were higher among patients coded as having meningococcal septicaemia (A39.1–A39.4, not A39.0; 4.1%) compared with those coded as having meningococcal meningitis (A39.0; 1.6%).

Notifications: Twenty-one deaths were recorded among the 622 cases of meningococcal disease notified to NNDSS for the 2 years 2006–2007 (case fatality rate of 3.4%). The age group distribution of the 12 notified cases who died in 2006 was comparable to that of the 12 deaths in 2006 in the AIHW National Mortality Database.

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Age and sex distribution

The highest meningococcal disease notification, hospitalisation and death rates occurred among children aged <5 years (Table 3.7.1), and the highest rates within this age group were among those <1 year of age (19.4 notifications, 34.4 hospitalisations and 2.03 deaths per 100,000 population). There was a second peak in notification rates (Figure 3.7.2) and hospitalisation rates (Figure 3.7.3) in the 15–19 year age group (3.9 and 5.0 per 100,000, respectively); rates were also elevated in the 20–24 year age group, but were lower in those ≥25 years of age (Table 3.7.1, Figures 3.7.2 and 3.7.3).

Figure 3.7.2: Meningococcal disease notification and death rates, Australia, 2005 to 2007,* by age group

Figure 3.7.2:  Meningococcal disease notification and death rates, Australia, 2005 to 2007, by age group

* Notifications where the date of diagnosis was between January 2006 and December 2007; deaths where the death was recorded between January 2005 and December 2006 on the AIHW National Mortality Database.

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Figure 3.7.3: Meningococcal disease hospitalisation rates, Australia, 2005/2006 to 2006/2007,* by age group

Figure 3.7.3:  Meningococcal disease hospitalisation rates, Australia, 2005/2006 to 2006/2007, by age group

* Hospitalisations where the date of separation was between July 2005 and June 2007.

Overall, there was a slight predominance of male cases (male:female rate ratio 1.1:1). This varied across age groups with generally higher rates in males aged 0–34 years and females aged ≥60 years.

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Geographical distribution

The pattern of notification and hospitalisation rates for meningococcal disease varied across the country. The highest notification and hospitalisation rates were in the Northern Territory (2.8 notifications per 100,000 population in both 2006 and 2007, and 5.3 hospitalisations per 100,000 population in 2005/2006). The lowest notification rates occurred in Tasmania and Western Australia in 2006–2007 (both were 1.0 per 100,000 population) (see also Appendix 6.2), while the lowest hospitalisation rate occurred in the Australian Capital Territory in 2005/2006–2006/2007 (1.7 per 100,000 population) (see also Appendix 6.3).

Notification rates were slightly lower in most states and territories in 2007 compared with 2006 (Appendix 6.2). Hospitalisation rates decreased between 2005/2006 and 2006/2007 across all jurisdictions (Appendix 6.3).

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Meningococcal serogrouping and vaccination

Meningococcal serogroup information was recorded for 83% of the 622 notified cases in 2006–2007 (Figure 3.7.4). There were 431 notified cases (1.0 per 100,000 population) of serogroup B meningococcal disease and 43 cases (0.1 per 100,000 population) of serogroup C disease. Between 2002 (before the national meningococcal C vaccination program commenced) and 2007, serogroup C disease notifications decreased by 92% from a peak of 225 in 2002 to 19 in 2007 (1.15 to 0.09 per 100,000 population) (Figure 3.7.4). By comparison, serogroup B disease notifications decreased by 27% from a peak in 2002 of 294 to 213 cases in 2007 (1.5 to 1.1 per 100,000 population). As a proportion of total notifications for meningococcal disease, serogroup C decreased from 33% in 2002 to 9% in 2007, while, over the same period, the proportion of serogroup B notifications increased from 40% to 70%; those where serogroup information was not available decreased slightly from 21% to 17%.

Figure 3.7.4: Meningococcal disease notifications, Australia, 1991 to 2007, by serogroup and year of diagnosis

Figure 3.7.4:  Meningococcal disease notifications, Australia, 1991 to 2007, by serogroup and year of diagnosis

Much of the decrease in serogroup C meningococcal disease notifications occurred among the age groups included in the national meningococcal C vaccination program during 2003–2006 (Figure 3.7.5a). A decrease in serogroup C notifications was also evident among the 20–24 year age group, which includes some people born during or after 1984 and eligible for free vaccine, as well as adults aged ≥25 years who were not included in the program (Figure 3.7.5b). Serogroup C notifications among children aged <1 year remained low in 2006–2007, with an average of 2 notifications per year (0.7 cases per 100,000 population), compared with an average of 38 serogroup B notifications per year (14.0 notifications per 100,000 population).

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Figure 3.7.5: Meningococcal serogroup C disease notification rates, Australia, 1999 to 2007, by age group* and year of diagnosis

(a)

Figure 3.7.5a:  Meningococcal serogroup C disease notification rates, Australia, 1999 to 2007, by age group and year of diagnosis

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(b)

Figure 3.7.5b:  Meningococcal serogroup C disease notification rates, Australia, 1999 to 2007, by age group and year of diagnosis

* Figure 3.7.5a shows the age groups included in the meningococcal C vaccination program from 1 January 2003.
Figure 3.7.5b shows other age groups. (Note: Cases aged 20–24 years in 2007 include those born during or after 1984 and included in the national meningococcal C vaccination program.)

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In 2006–2007, meningococcal C vaccination status was recorded for 35 (81%) of the 43 notified cases of serogroup C disease and 15 of the 16 cases aged ≤19 years. There were just three reports of vaccine failure in children, aged 3 years, 14 years and 15 years at disease onset.

During 2006–2007, there was some heterogeneity between jurisdictions in the relative notification rates of serogroup B and serogroup C meningococcal disease (Figure 3.7.6), with the ratio of serogroup B to serogroup C varying from 37:1 in Western Australia to 5.5:1 in New South Wales. Following the introduction of the national meningococcal C vaccination program in January 2003, there was a significant reduction in serogroup C notification rates across most states and territories, with the largest reductions in Tasmania and Victoria (Figure 3.7.7).

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Figure 3.7.6: Meningococcal disease notification rates, Australia, 2006 to 2007,* by state or territory and serogroup

Figure 3.7.6:  Meningococcal disease notification rates, Australia, 2006 to 2007, by state or territory and serogroup

* Notifications where the date of diagnosis was between January 2006 and December 2007.

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Figure 3.7.7: Meningococcal serogroup C disease notification rates, Australia, 2006–2007* compared with 2002, by state or territory

Figure 3.7.7:  Meningococcal serogroup C disease notification rates, Australia, 2006-2007 compared with 2002, by state or territory

* Notifications where the date of diagnosis was between January 2006 and December 2007.

† Notifications where the date of diagnosis was between January 2002 and December 2002.

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Comment

The incidence of meningococcal disease in Australia increased continuously between 1991 and 2002. Since 2003, there has been a marked and sustained decrease in meningococcal disease notifications, hospitalisations and deaths5 following the introduction of the routine and catch-up meningococcal C vaccination programs for those born after 1983.

The largest reduction in notifications and deaths occurred for serogroup C disease and those where serogroup information was not available (suggesting many were serogroup C). Over the same period, notifications for serogroup B have declined slightly, presumably related to known natural variations in meningococcal disease epidemiology over time.5,6 Notifications for other serogroups, mainly W135 and Y, have remained relatively stable over the 2002–2007 period. Reassuringly, these data, and those reported elsewhere for Australia and internationally, show that there has been no evidence of serogroup replacement following mass meningococcal C immunisation programs.7–10

The decrease in serogroup C disease notifications occurred across Australia and among all age groups included in the mass vaccination program, particularly those aged 15–19 years at the time of diagnosis. There was also a smaller decrease in serogroup C notifications among adults not included in the national vaccination program, while rates among children <1 year of age remained very low. This suggests protection across all age groups through herd immunity, primarily as a consequence of the mass immunisation program and, to a lesser extent, from a reduction in natural exposure to pharyngeal infection/colonisation with serogroup C.11–14

Between 2003 and 2007, there were six recorded cases of vaccine failure in Australia, including the three reported here.15,16 Four were aged 1–4 years and two were adolescents. A similar low rate of vaccine failure among young children has been observed in The Netherlands,17 which, like Australia, routinely immunises children in the 2nd year of life. In contrast, the UK has reported considerably higher levels of vaccine failure, particularly among those immunised during the first 6 months of life.18,19 A recent serologic study in the UK reported that persistence of bactericidal antibody was correlated with age at vaccination, with higher levels of protection 5 years after receipt of conjugate meningococcal vaccine among children aged ≥10 years at the time of vaccination compared with younger age groups.20 This finding suggests that the low number of vaccine failures seen among Australian adolescents is related to a strong immunogenic response in those vaccinated through mass school- and community-based immunisation programs during 2003 and 2004 as well as herd immunity. Ongoing surveillance and reporting of the vaccination status of cases of meningococcal serogroup C disease is essential to monitor vaccine effectiveness over the longer term and inform Australian meningococcal C immunisation policy.

Currently, as reported here and by the National Neisseria Network,7 the great majority of the burden of invasive meningococcal disease in Australia is now due to serogroup B disease, which contributes approximately 70% of meningococcal disease cases. Those at particular risk of meningococcal serogroup B disease are infants <1 year of age and, as reported elsewhere, Indigenous Australians.21,22 The high burden of serogroup B meningococcal disease in these risk groups emphasises the importance of early recognition and appropriate clinical management of disease and the need for the development of a vaccine to reduce the significant morbidity and mortality. Several candidate serogroup B vaccines are under investigation;23 however, it will be some time yet before a universal serogroup B vaccine appropriate for use in Australia becomes available for consideration.

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References

1. Granoff DM, Harrison LH, Borrow R. Meningococcal vaccines. In: Plotkin SA, Orenstein WA, Offit PA, eds. Vaccines. 5th edn. Philadelphia, PA: Saunders Elsevier, 2008.

2. Apicella MA. Neisseria meningitidis. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. Volume 2. 6th edn. Philadelphia: Elsevier Churchill Livingstone, 2005.

3. Communicable Diseases Network Australia. Surveillance case definitions for the Australian National Notifiable Diseases Surveillance System. 2004. Available from: http://www.health.gov.au/internet/main/publishing.nsf/Content/cdna-casedefinitions.htm Accessed on 24 August 2009.

4. Cohen NJ. Introduction of the National Meningococcal C Vaccination Program. Commun Dis Intell 2003;27(2):161–162.

5. Simpkins D, Wood N, Jelfs J, McIntyre PB, Menzies R, Lawrence G, et al. Modern trends in mortality from meningococcal disease in Australia. Pediatr Infect Dis J 2009;28(12):1119–1120.

6. Patel MS. Australia’s century of meningococcal disease: development and the changing ecology of an accidental pathogen. Med J Aust 2007;186(3):136–141.

7. Australian Meningococcal Surveillance Programme. Annual report of the Australian Meningococcal Surveillance Programme, 2007. Commun Dis Intell 2009;33(1):1–9.

8. Trotter CL, Ramsay ME, Gray S, Fox A, Kaczmarski E. No evidence for capsule replacement following mass immunisation with meningococcal serogroup C conjugate vaccines in England and Wales. Lancet Infect Dis 2006;6(10):616–617.

9. Siu T, Tang W, Dawar M, Patrick DM. Impact of routine immunization using meningococcal C conjugate vaccine on invasive meningococcal disease in British Columbia. Can J Public Health 2008;99(5):380–382.

10. Slinko VG, Sweeny A. Reduction in invasive meningococcal disease in Queensland: a success for immunisation. Commun Dis Intell 2007;31(2):227–232.

11. Booy R, Jelfs J, El Bashir H, Nissen MD. Impact of meningococcal C conjugate vaccine use in Australia. Med J Aust 2007;186(3):108–109.

12. Maiden MC, Stuart JM. Carriage of serogroup C meningococci 1 year after meningococcal C conjugate polysaccharide vaccination. Lancet 2002;359(9320):1829–1830.

13. Dellicour S, Greenwood B. Systematic review: impact of meningococcal vaccination on pharyngeal carriage of meningococci. Trop Med Int Health 2007;12(12):1409–1421.

14. Gray SJ, Trotter CL, Ramsay ME, Guiver M, Fox AJ, Borrow R, et al. Epidemiology of meningococcal disease in England and Wales 1993/94 to 2003/04: contribution and experiences of the Meningococcal Reference Unit. J Med Microbiol 2006;55(Pt 7):887–896.

15. Brotherton J, Wang H, Schaffer A, Quinn H, Menzies R, Hull B, et al. Vaccine Preventable Diseases and Vaccination Coverage in Australia, 2003 to 2005. Commun Dis Intell 2007;31(Suppl):S1–S152.

16. Shaw KA, McGregor AR, Taylor RE, Williamson J, Misrachi A, Coleman DJ, et al. Meningococcal vaccine failure in conjunction with an unusual meningococcal cluster in southern Tasmania. Commun Dis Intell 2005;29(2):160–164.

17. de Greeff SC, de Melker HE, Spanjaard L, Schouls LM, van DerEnde A. Protection from routine vaccination at the age of 14 months with meningococcal serogroup C conjugate vaccine in the Netherlands. Pediatr Infect Dis J 2006;25(1):79–80.

18. Trotter CL, Andrews NJ, Kaczmarski EB, Miller E, Ramsay ME. Effectiveness of meningococcal serogroup C conjugate vaccine 4 years after introduction. Lancet 2004;364(9431):365–367.

19. Borrow R, Miller E. Long-term protection in children with meningococcal C conjugate vaccination: lessons learned. Expert Rev Vaccines 2006;5(6):851–857.

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20. Snape MD, Kelly DF, Lewis S, Banner C, Kibwana L, Moore CE, et al. Seroprotection against serogroup C meningococcal disease in adolescents in the United Kingdom: observational study. BMJ 2008;336(7659):1487–1491.

21. Menzies R, Turnour C, Chiu C, McIntyre P. Vaccine Preventable Diseases and Vaccination Coverage in Aboriginal and Torres Strait Islander People, Australia 2003 to 2006. Commun Dis Intell 2008;32(Suppl):S2–S67.

22. Massey P, Durrheim D. Aboriginal and Torres Strait Islander peoples at higher risk of invasive meningococcal disease in NSW. N S W Public Health Bull 2008;19(5–6):100–103.

23. Holst J. Strategies for development of universal vaccines against meningococcal serogroup B disease: the most promising options and the challenges evaluating them. Hum Vaccin 2007;3(6):290–294.

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