Vaccine Preventable Diseases and Vaccination Coverage in Australia, 2003 to 2005

Pneumococcal disease

Disclaimer: This is the fourth report on vaccine preventable disease and vaccination coverage in Australia, and is produced by the National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases and the Australian Institute of Health and Welfare on behalf of the Australian Government Department of Health and Ageing published as a supplement to the Communicable Diseases Intelligence journal Volume 31, June 2007.

Page last updated: 20 July 2007

Pneumococcal disease is caused by the bacterium Streptococcus pneumoniae (pneumococcus). Pneumococci are frequently isolated from the upper respiratory tract and can spread directly from the nasopharynx to cause infection in other parts of the respiratory tract (otitis media, sinusitis, pneumonia) or enter the bloodstream. Following bloodstream invasion, clinical manifestations include meningitis, pneumonia and infection at a number of less common sites, as well as septicaemia without focal infection. Invasive pneumococcal disease (IPD) is defined as a sterile site isolate of Streptococcus pneumoniae, usuallyfrom blood. In the absence of a sterile site isolate, a presumptive diagnosis of pneumococcal pneumonia may be based on a sputum isolate of Streptococcus pneumoniae and/or clinical features such as the chest x-ray appearance and prompt response to antibiotic therapy.156

Case definitions

Notifications

Invasive pneumococcal disease has been notifiable in the Northern Territory since 1995 and in Queensland since 1997. From January 2001, invasive pneumococcal disease became notifiable Australia wide, with cases identified by:

a) Isolation of Streptococcus pneumoniae by culture from a normally sterile site

or

b) Detection of Streptococcus pneumoniae from a normally sterile site by nucleic acid testing.

Hospitalisations

The ICD-10-AM codes used to identify hospitalisations were: G00.1 (pneumococcal meningitis); A40.3 (pneumococcal septicaemia) (together considered to be a proxy for invasive pneumococcal disease) and J13 (pneumococcal pneumonia). To avoid double counting, cases were identified in a hierarchical fashion. First, all those with code G00.1 were classified as meningitis, then those without G00.1 but with A40.3 were classified as septicaemia without meningitis, and then those with neither of these codes but with code J13 were counted as pneumococcal pneumonia.

Deaths

ICD-10 codes G00.1, A40.3 and J13 were used to select deaths from IPD.

Top of page

Secular trends

A total of 6,303 notifications of invasive pneumococcal disease were received for the three year period (2,237 in 2003, 2,377 in 2004 and 1,689 in 2005), an average annual notification rate of 10.5 per 100,000 (Table 15). In all years, there was a winter peak in pneumococcal notifications in August (Figure 29).

The total number of hospitalisations coded as pneumococcal meningitis, septicaemia or pneumonia between July 2002 and June 2005 was 9,543, an average annual rate of 16.0 per 100,000 (Table 15). In 69% of these, pneumococcal disease was recorded as the principal cause of the hospitalisation. Hospitalisations coded as meningitis or septicaemia accounted for 33% of total episodes giving a hospitalisation rate of 5.2 per 100,000. The median number of hospitalisations per month was 73 for meningitis or septicaemia (predominantly septicaemia) and ranged from 31 to 170. For pneumococcal pneumonia, the median number of hospitalisations per month was 161 (range 77–346). Hospitalisations showed a clear winter peak each year between July and September (Figure 29).

Figure 29. Pneumococcal disease notifications and hospitalisations, Australia, January 1996 to December 2005,* by month of diagnosis or admission

Figure 29. Pneumococcal  disease notifications and hospitalisations, Australia, January 1996 to December 2005, by month of diagnosis or admission

* Notifications where the month of diagnosis was between January 2001 and December 2005;
hospitalisations where the month of admission was between 1 January 1996 and 30 June 2005.
Hospitalisations include pneumonia, meningitis and septicaemia.

Notification rates and hospitalisation rates decreased in 2005 compared to previous years, coinciding with the commencement of universal funded vaccination for infants and the elderly. Notification rates in those aged less than two years were 66% lower in 2005 compared to the average for the previous three years (Figure 30), and 24% lower in those age 65 and over (Figure 31). There were also decreases in age groups not targeted for vaccination; 41% in those aged 2–14 years, 16% in those 15–49 years and 4% in those aged 50–64 years. Hospitalisation rates for the 2004/2005 financial year were also lower than the average of the previous five years, by 37% for those aged less than two years, 22% for those aged 65 and over, and 5% to 25% in other age groups.

Figure 30. Pneumococcal disease notification rates, Australia, 2002 to 2005,* by age group

Figure 30. Pneumococcal  disease notification rates, Australia,  2002 to 2005, by age group

* Notifications where the date of diagnosis was between 1 January 2002 and 31 December 2005.

Figure  31. Pneumococcal disease  notification rates, Australia,  2002 to 2005, by age group (excluding <2 years)

* Notifications where the date of diagnosis was between 1 January 2002 and 31 December 2005.

Top of page

Severe morbidity and mortality

A total of 93,691 hospital bed days (average 31,230 days per year) was recorded for hospital separations with an ICD-10-AM code corresponding to pneumococcal meningitis, septicaemia or pneumonia. The median length of stay increased with age in all categories of infection (Table 15). The average length of stay was greater than the median. For pneumococcal meningitis, the average was 13.5 days in all age groups, higher than that for septicaemia (10.4) or pneumonia (9.3).

Table 15. Pneumococcal disease notifications, hospitalisations and deaths, Australia, 2002 to 2005,* by age group

Age group
(years)
Notifications
3 years
(2003–2005)
Hospitalisations
3 years
(July 2002–June 2005)
LOS per
admission
(days)
Deaths
2 years
(2003–2004)
n Rate n§ (M/S)|| Rate‡,§ (M/S)‡,|| Median§ (M/S)|| n§ (M/S)|| Rate‡,§ (M/S)‡,¶
0–4
1,712
45.2
1,396
(831)
36.8
(21.9)
3.0
(3.0)
13
(11)
0.5
(0.4)
5–14
258
3.2
302
(129)
3.7
(1.6)
3.0
(3.0)
0
(0)
0.0
(0.0)
15–24
247
3.0
357
(86)
4.4
(1.1)
4.0
(5.0)
2
(1)
0.04
(0.02)
25–59
1,935
6.6
3,255
(908)
11.1
(3.1)
5.0
(8.0)
20
(10)
0.1
(0.1)
60+
2,151
20.4
4,233
(1,161)
41.2
(11.3)
8.0
(9.0)
47
(16)
0.7
(0.2)
All ages
6,303
10.5
9,543
(3,115)
16.0
(5.2)
6.0
(7.0)
82
(38)
0.2
(0.1)

* Notifications where the month of diagnosis was between January 2003 and December 2005; hospitalisations where the month of separation was between 1 July 2002 and 30 June 2005; deaths where the date of death was recorded between 2003 and 2004.

† LOS = length of stay in hospital.

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

§ All pneumococcal disease.

|| (M/S) = meningitis and septicaemia.

Of the 82 registry-reported pneumococcal deaths in 2003 to 2004, 44 (54%) were from pneumonia, 20 (24%) from meningitis and 18 (22%) from septicaemia. Mortality rates from meningitis and septicaemia were highest in the very young and the elderly, while the pneumonia death rate was highest in the elderly (Table 15).

There were 361 deaths from pneumococcal disease in notified cases reported to NNDSS between 2003 and 2005, 6% of notified cases. The death rate increased with age, highest at 20% for those aged 85 years and over and 13% for those aged 65 years and over.

Top of page

Age and sex distribution

Males had higher notification and hospitalisation rates compared to females in all age groups, and all ages combined (1.3 times and 1.4 times higher, respectively). Notification and hospitalisation rates were highest in the very young and the very old, although rates in infants decreased to a greater extent than other age groups in 2005 compared to previous years (Figure 30 and Figure 31). The hospitalisation rate for each age group varied with the focus of infection (Figure 32). For meningitis, rates were highest in those aged less than five years (6 per 100,000). By contrast, the incidence of hospitalisation for septicaemia without meningitis was also high in young children (16.0), but in adults increased with age to be highest in the elderly (24.7 in those 85 years and over).

When total hospitalisations (meningitis, septicaemia and pneumonia) were considered, adults aged 60 years and over had the highest total rate of hospitalisation (41.2 per 100,000, Table 15).

Figure 32. Pneumococcal meningitis, septicaemia and pneumonia hospitalisation rates,* Australia, 2002 to 2005, by age group

Figure 32. Pneumococcal  meningitis, septicaemia and pneumonia hospitalisation rates, Australia, 2002  to 2005, by age group

* Hospitalisations where the month of separation was between 1 July 2002 and 30 June 2005.

Top of page

Geographical distribution

The average annual notification rate was 10.5 per 100,000 for Australia, highest in the Northern Territory (39.4, 3.8 times higher than the national rate) and ranged from 7.8 to 13.0 in other jurisdictions. A similar distribution was seen in the hospitalisation rate for pneumococcal meningitis or septicaemia (national rate 5.2), which was higher in the Northern Territory (22.1, 4.3 times higher than the national rate), with little difference between the other jurisdictions (4.2 to 5.8).

Pneumococcal typing

Data on the serotype of cases reported to NNDSS were available from 6,749 of 8,769 cases (77%) from 2002 to 2005, the period when surveillance has been carried out in all jurisdictions. In the pre-vaccination period of 2002 to 2004, 73% of serotyped cases were caused by serotypes contained in the 7-valent conjugate pneumococcal vaccine (7vCPV), used in infants, and 85% of serotyped cases in children aged less than two years. Cases caused by serotypes in the 23-valent pneumococcal polysaccharide vaccine (23vPPV), used in high-risk children and the elderly, were 92% of the total and 90% in those aged 65 years and over. In 2005, the notification rate in 7vPCV-type cases decreased by 80% in those aged less than two years, compared to the average of the previous three years (Figure 33), and by 43% in all ages combined (Table 16). Decreases were seen in all age groups, but they were less marked in younger adults. There was little change in all-age notification rates of cases with serotypes contained in the 23vPPV but not in the 7vPCV (23v-non-7v types), or in serotypes not in any vaccine, in 2005 compared to the previous three years. In those aged 65 years and over, there were decreases in all serotype groupings, i.e. 7vPCV types, 23v-non-7v types, and non-vaccine types. In age groups not included in universal funded vaccination programs (2–64 years), notification rates were higher in 2005 compared to 2002 to 2004 for serotypes not included in the 7vPCV, but total rates were lower, due to decreases in 7vPCV-type cases.

Figure 33. Notification rates of cases with serotypes contained in the 7-valent pneumococcal conjugate vaccine (7vPCV), versus rates for other serotypes, Australia, 2002 to 2005*

Figure 33. Notification rates of cases with serotypes contained in  the 7-valent pneumococcal conjugate vaccine (7vPCV), versus rates for other  serotypes, Australia, 2002 to 2005

* Notifications where the date of diagnosis was between 1 January 2002 and 31 December 2005.

Table 16. Invasive pneumococcal disease notification rates,* Australia, 2005 as a percentage of average annual rates from 2002 to 2004, by serotype grouping

Age group
(years)
Serotype
7v 23v-non-7v Non-23v§ TotalII
<2
20
99
62
34
2–14
46
116
102
59
15–49
84
114
139
84
50–64
81
109
170
96
65+
69
85
62
76
All ages
57
103
98
70

* Notifications to the National Notifiable Diseases Surveillance System, per 100,000 population.

† Serotypes contained in the seven-valent pneumococcal conjugate vaccine (7vPCV); 4, 6B, 9V, 14, 18C, 19F, 23F.

‡ Serotypes contained in the 23-valent pneumococcal polysaccharide vaccine but not in the 7vPCV; 1, 2, 3, 5, 7F, 8, 9N, 10A, 11A, 12F, 15B, 17F, 19A, 20, 22F, 33F.

§ Serotypes not included in either vaccine.

II Includes untyped cases.

Top of page

Vaccination status

Data on vaccination status were available for 89 (52%) of the 172 cases recorded on NNDSS in children eligible for a full course of the funded universal vaccination and catch-up programs (from 1 January 2005, children born from January 1 2003 and aged more than 6 months at disease onset). Of those, 22 (25%) were reported to be fully vaccinated, and this was validated by vaccination records for 18. Partially completed vaccination was reported by 26 (29%) and 41 (46%) were unvaccinated. In cases aged 65 years and over, vaccination status was reported for 936 of 1,782 (53%). Of those, 35% were reported as fully vaccinated, 11% partially vaccinated and 55% unvaccinated. Information on the source of vaccination status data was available in 709 (76%) of those records, and 94% were reported to be from written vaccination records.

Comment

Invasive pneumococcal disease has historically been a disease predominantly affecting the very young, the very old and those with certain chronic diseases or other high-risk conditions. In particular, much higher rates of disease have been reported in Aboriginal and Torres Strait Islander young children and adults compared to non-Indigenous Australians.157–159 Vaccination with the 23vPPV has been funded nationally since 1999 for Aboriginal and Torres Strait Islander adults aged 50 years and over, and those aged 15–49 years with high-risk conditions.3 Nationally funded 7vPCV vaccination commenced in 2001 for all Aboriginal and Torres Strait Islander infants and other infants with high-risk conditions.3 In 2005, the 7vPCV was funded for all Australian infants and the 23vPPV for all aged 65 years and over.

Reports on IPD national notification data have been published since 2001.160–163 A decrease in rates in Indigenous children following the targeted infants vaccination program has been previously reported, with a threefold higher rate in Indigenous compared to non-Indigenous children under two years of age in 2001 reduced to parity in 2004.163 Data in this report suggest a noticeable impact in the first year of universal infant vaccination, as the IPD notification rate declined by 66% in those aged less than two years in 2005 compared to the three previous years, and 80% in cases with serotypes contained in the vaccine. Smaller decreases occurred in all other age groups, but these should be interpreted with caution due to the smaller numbers of cases in these age groups. Hospitalisation rates were lower in 2004/2005 compared to previous years, although this included only the first six months of the funded vaccination program. There were decreases in all age groups, but the greatest decrease was seen in infants (37%). Similar impacts have been seen in the USA following the commencement of universal infant vaccination in 2001; an estimated 25,000 cases were prevented in 2003, and 49% of those were in non-immunised age groups, presumably due to reductions in nasopharyngeal carriage and, therefore, fewer transmissions to the unvaccinated.164

Hospitalisation rates for pneumococcal disease were approximately 30% higher than IPD notification rates. The hospitalisation codes selected were less specific for identifying invasive disease than the IPD case definition, as they include pneumococcal pneumonia without bacteraemia. In addition, hospitalisations coded as due to bacteraemia have been previously shown to have low sensitivity.165 Hospitalisations for pneumococcal meningitis and septicaemia number approximately half those of IPD notifications. It is, therefore, likely that pneumococcal disease hospitalisations are under-estimated by these data.

In addition to preventing IPD, the 7vPCV has been shown to have some efficacy against the much more common manifestations of non-bacteraemic pneumococcal pneumonia and otitis media.166,167 Therefore, decreases in IPD notification rates represent only a proportion of the total impact of this vaccine. Continued monitoring of hospitalisation rates for pneumococcal pneumonia will be valuable in monitoring some of this impact. The decrease in hospitalisation rates from 1996 to 1999 shown here is likely to be related to coding practices rather than an actual decrease in incidence, as all-cause pneumonia hospitalisation rates did not change over time (data not shown). However, the more stable pattern from 1999 provides a useful baseline for monitoring the impact of vaccination in the future.

Concerns about replacement disease by serotypes not contained in the vaccine have been expressed.167 In the USA, some replacement IPD appears to have occurred, but there is still a substantial overall decrease in IPD notifications.164 The data presented here for Australia on the first year of the vaccination program suggest the possibility of some replacement disease in unvaccinated age groups, but a substantial overall decline in IPD rates. It will be important to monitor this closely in the future.

The 23vPPV has been shown to be effective against IPD in elderly populations without high rates of risk factors, but effectiveness against nasopharyngeal carriage and pneumococcal pneumonia have not been established.43,168 Low vaccine effectiveness has been found in overseas studies in those with chronic disease and high-risk conditions, including indigenous populations.169 Vaccination programs for Indigenous adults from the early 1990s in the Kimberley and mid-1990s in northern Queensland coincided with reductions in IPD incidence in Indigenous adults in those regions.158,170 However, no decrease in incidence has been seen in Northern Territory Indigenous adults, despite vaccination programs targeting those aged 50 years and over since 1995 and all Indigenous adults since 2000.171 Funded vaccination for all Victorians aged 65 years and over since 1998 has been effective in that state,172 and a similar impact could be expected nationally. The data reported here include the period up to the end of the first year of nationally funded vaccination for those aged 65 years and over. Although decreases were seen in hospitalisation and notification rates in this age group in 2005 compared to previous years, the decreases in notifications occurred across a wide range of serotypes and may be attributable to adult vaccination, herd immunity from childhood vaccination, and/or other reasons. It will be necessary to examine this in later years when more data become available. Reported deaths were predominantly in adults, with the highest death rates in the oldest age groups. There were 2.9 times as many pneumococcal deaths reported through NNDSS compared to registry reports, even though registry deaths included the broader category of all pneumococcal pneumonia, suggesting under-reporting of this cause of death by this mechanism.

The Northern Territory has the highest disease burden and there is little difference between the other jurisdictions. Disparities between Indigenous and non-Indigenous children may re-emerge following universal vaccination, due to higher rates of non-vaccine type disease in Indigenous people.163 New conjugate vaccines with greater serotype coverage may be necessary to address this and the persistently high rates in Northern Territory Indigenous adults.

Document download

This publication is available as a downloadable document.

Vaccine Preventable Diseases and Vaccination Coverage in Australia, 2003 to 2005(PDF 1622 KB)