A print friendly PDF version is available from this Communicable Diseases Intelligence issue's table of contents.

Introduction

In March 1999, a workshop titled 'Pneumococcal disease in Australia' was held at the National Centre for Immunisation Research and Surveillance of Vaccine Preventable Disease in Sydney. A summary of the workshop¹ and recommendations for surveillance² were subsequently published in Communicable Diseases Intelligence in April 2000. More detailed papers arising from presentations by a wide range of Australian experts appeared later that year as a supplement of the Medical Journal of Australia. The papers in the supplement described the epidemiology of invasive pneumococcal disease (IPD) in areas of Australia with a relatively low proportion (metropolitan New South Wales, Victoria) and a relatively high proportion (Northern Territory and Western Australia) of the population who are Aborigines or Torres Strait Islanders. The most prominent issues identified were the high incidence of IPD among Aboriginal children, particularly in Central Australia, associated with a more diverse range of serotypes than non-Indigenous children; the morbidity and mortality of IPD, particularly meningitis; and increasing levels of antibiotic resistance among strains of Streptococcus pneumoniae.

At the time of the first meeting, pneumococcal disease in young children was not vaccine-preventable as the only vaccine then available, the 23-valent polysaccharide vaccine, 23vPPV) is poorly immunogenic under the age of 2 years. Subsequently, the seven-valent conjugate pneumococcal vaccine (7vPCV) was approved for use in Australia by the Therapeutic Goods Administration in December 2000. A Pneumococcal Working Party, jointly chaired by the Australian Technical Advisory Group on Immunisation and the Communicable Diseases Network Australia had been established earlier in 2000. The Pneumococcal Working Party recommended urgent implementation of a publicly funded vaccination program with 7vPCV for children at highest risk of IPD, primarily those with predisposing medical conditions aged under 5 years and all Indigenous children aged under 2 years. The program commenced in July 2001 in Central Australia and was progressively implemented in other states and territories over the next 6 months. At the time of the first workshop, invasive pneumococcal disease was notifiable only in the Northern Territory (since 1995) and Queensland (since 1996).² In January 2001, the Communicable Diseases Network Australia agreed to make IPD a notifiable disease in all Australian jurisdictions, with enhanced surveillance systems implemented and funded by the end of 2001. The second national workshop in November 2002 provided an opportunity to evaluate the first year of enhanced surveillance and the 7vPCV vaccination program and to learn from the experience following the introduction of universal 7vPCV vaccination of children under 2 years of age in the United States of America at the end of 2000.

Top of page

Day 1. Surveillance of invasive pneumococcal disease

Long term population-based surveillance in the United States of America and Australia

United States of America

Cynthia Whitney, a medical epidemiologist from the Centers for Disease Control and Prevention Atlanta, reviewed the current epidemiology of pneumococcal disease in the USA and the impact of the conjugate vaccine. Surveillance of IPD is based on 10 sentinel areas (counties, cities or states) with a total population of 20 to 24 million people. Cases of IPD occurring in these sentinel areas are actively followed up and isolates are collected and analysed for serotype and antimicrobial resistance at the Centers for Disease Control and Prevention or reference laboratories. Surveillance is aimed at assessing vaccine effectiveness. Early assessments indicate a reduction of the order of 70 per cent in the incidence of IPD in children aged less than 2 years. Vaccine failures have been documented in 129 cases of which 47 per cent were cases with non-vaccine serotypes, 37 per cent with vaccine serotypes and 17 per cent with vaccine-related serotypes. Among the 48 cases with vaccine serotypes, only 11 were fully vaccinated and the most common serotype isolated was 6B (n=6). The majority of children who were vaccine failures had other underlying conditions predisposing to pneumococcal infection.

North Queensland

Jeffrey Hanna, Director of the Tropical Public Health Unit based in Cairns, reported on enhanced surveillance of IPD in Far North Queensland since 1992, subsequently expanded to include the whole of north Queensland.³ The incidence of IPD in Indigenous children under 2 years of age (297 cases per 100,000 population) is similar to that reported from the Top End of the Northern Territory (326 cases per 100,000 population) but dwarfed by the incidence among Aboriginal children in Central Australia (1,534 cases per 100,000 population). Importantly, the incidence in Far North Queensland of pneumococcal meningitis among Indigenous children (56 cases per 100,000 population) was higher than in non-Indigenous children (17 cases per 100,000 population) and occurred at a significantly younger age (median 0.5 years) than non-Indigenous children (1.0 years). In Indigenous children, only 62 per cent of isolates had serotypes contained in the 7vPCV, compared with 88 per cent among non-Indigenous children.

Metropolitan New South Wales

Peter McIntyre, Deputy Director of the National Centre for Immunisation Research and Surveillance, updated to 2001 the earlier report to 1999 of enhanced surveillance of IPD in metropolitan New South Wales by a laboratory network.⁴ The overall incidence of IPD in children aged under 2 years (100 cases per 100,000 population) and pneumococcal meningitis (10 cases per 100,000 population) and the serotype distribution (90 per cent included in 7vPCV) were unchanged. In children less than 5 years of age, additional medical risk factors (extreme prematurity, all premature infants with chronic lung disease and all children with Downs syndrome, diabetes mellitus and cystic fibrosis) were associated with increased numbers of cases. A case-control study in this population has shown that attending child care is most important as a risk factor for IPD in the first 3 months after commencement. Only 15 IPD cases were identified as Indigenous during the study period, giving a very similar incidence to non-Indigenous children. This may suggest that the incidence of IPD in Indigenous children living in an urban setting is lower than in rural and remote settings, but is limited by deficiencies in identifying Indigenous children in urban areas and needs further investigation.

Enhanced surveillance of notifiable invasive pneumococcal disease in states and territories since 2001

Short presentations were made on national data collected from enhanced surveillance for IPD in 2001 and reports of IPD surveillance activities in 2002 in each state and territory. The national report for 2001 has recently been published⁵ and the abstracts of each state and territory's presentation are included in the appendix to this report.

Top of page

Laboratory issues

Lyn Gilbert, Chair of the Laboratory Sub-group of the Pneumococcal Working Party, reviewed the contribution of laboratories to the surveillance of IPD, particularly in measuring the impact of vaccination on serotype distribution and the prevalence of antibiotic resistance. Maintenance of laboratory networks for forwarding IPD isolates and for serotyping and reporting is resource intensive. Current resources will not be sufficient for expanded antimicrobial susceptibility testing. There are a number of more sophisticated methods for serotyping and molecular typing of pneumococcal strains under development. The potential for molecular serotyping of S. pneumoniae was discussed in the context of a pilot project which has shown these new techniques correlate well with traditional serological typing, with the potential for micro-array technology to automate typing and antimicrobial susceptibility. In addition, multi-locus sequence-typing based on variations in seven S. pneumoniae genes, provides a tool for measuring the molecular epidemiology of antimicrobial resistance and serotype dynamics.

Surveillance of pneumococcal vaccine coverage

While childhood immunisation coverage rates are now monitored in the Australian Childhood Immunisation Register (ACIR), no national register exists for adult vaccines. Hence, there is considerable uncertainty about the proportion of older Australians receiving the pneumococcal polysaccharide vaccine.

Coverage estimates for 23vPPV - Victoria and Australia

Ross Andrews, who is currently evaluating the Victorian funded 23vPPV program, described survey methods aimed at estimating pneumococcal polysaccharide vaccine coverage. In Victoria, vaccine has been offered free of charge to all residents aged 65 years or more since 1997.⁶ There are methodological problems in measuring pneumococcal vaccine coverage in older persons by telephone survey. A computer-assisted telephone interview validated against physician records in Victoria has estimated coverage for over 65 year olds receiving the vaccine within the past 5 years, to be between 47 and 51 per cent. Coverage increased over the 5 years 1996 to 2000. By contrast, using Pharmaceutical Benefits Scheme data the coverage in the rest of Australia was estimated to be 25 to 28 per cent, but is also a significant increase over estimates from 1996. In Victoria, preliminary data from a National Health and Medical Research Council funded hospital-based case-cohort study suggest that 23vPPV has an effectiveness of 80 per cent when measured against an outcome of hospitalisation for pneumonia.

Coverage estimates for 7vPCV

Peter McIntyre described the use of the ACIR to measure coverage of eligible children with the conjugate pneumococcal vaccine. ACIR data show that little vaccine was distributed outside the jurisdictions with the highest rural and remote Indigenous populations (the Northern Territory, Western Australia and Queensland) before 2002, with a progressive increase in 2002. Although the ACIR collects information on the Indigenous status of children, these data have not been available or have been poorly utilised until recently. If all doses recorded on the ACIR are assumed to have been given to Indigenous children, then of the estimated Indigenous birth cohort, over 90 per cent of the Northern Territory, 67 per cent of the Western Australian and Queensland and 44 per cent of other jurisdictions received 7vPCV in the first quarter of 2002. The availability of an Indigenous status indicator by state or territory on the ACIR will soon allow more accurate estimates. The currently available data from the ACIR, and other data presented at the meeting from the Northern Territory, Western Australia and Queensland, suggest that coverage of 7vPCV has been satisfactory in the highest risk populations.

Surveillance of invasive pneumococcal disease - where to from here?

The first day concluded with an animated discussion on the needs of surveillance of IPD in the future. The present needs to improve the Commonwealth funded enhanced surveillance for IPD were described by Vicki Krause. These include capturing all incident cases; improving links with laboratories; collecting more complete data on Indigenous status; more broadly defining risk factors for pneumococcal disease; and measuring outcomes, including deaths, more accurately. Beyond these immediate needs, the groups discussed the sustainability of enhanced surveillance nationwide in the context of limited resources. Cynthia Whitney described the USA experience of using sentinel areas in place of nationwide surveillance and some of the limitations of this method. In most Australian states (except the Northern Territory and Western Australia and the far north of Queensland), there will be little measurable effect of the conjugate vaccine on rates of pneumococcal disease, since the majority of children in these regions are not eligible for free vaccine under the current schedule. The meeting concluded that high quality enhanced surveillance should be supported in the Northern Territory, rural Western Australia and Far North Queensland. Surveillance in other areas should be reviewed in light of other priorities. Data from Victoria on the impact of the polysaccharide vaccine should continue to be collected to provide information relevant to the use of this vaccine in controlling pneumococcal disease in the elderly elsewhere in Australia. The costs of adding adult vaccine coverage data to the ACIR are probably prohibitive. Novel methods of increasing adult vaccine coverage, such as linking pneumococcal vaccination to annual influenza vaccinations, should be considered.

Top of page

Day 2 - Pneumococcal vaccines and their impact

The second day of the meeting focussed on the impact of pneumococcal vaccines on IPD. The coverage and impact of polysaccharide vaccines in the USA, and in non-Indigenous and Indigenous adults in regions of Australia, was reviewed first followed by similar data on 7vPCV.

Pneumococcal polysaccharide vaccines

Issues in the United States of America

Cynthia Whitney reviewed data on the use of the polysaccharide vaccine in the USA, where the 23-valent vaccine has been in use since 1983. As in Australia, the vaccine is recommended for all persons aged 65 years or more and for at-risk groups aged 2 years or more. There have been concerns about an increase in pneumococcal disease following vaccination with 23vPPV in HIV-infected people with advanced disease.^7,8 In the USA, the 23-valent vaccine appears to protect HIV-infected people against pneumococcal disease without adverse effects, but efficacy is greatest when CD4+ cell counts are over 500. Therefore vaccination should be as early as possible after seroconversion or following immune-reconstitution with antiretroviral therapy. The question of re-vaccination of the elderly using 23-valent vaccine is being addressed. The duration of vaccine protection is difficult to measure in elderly populations who have a high prevalence of immunosuppressive disease and a high usage of medications. Currently, re-vaccination is recommended every 5 years; however, the safety of re-vaccination needs to be assessed since local reactions to the vaccine become more significant. Coverage in the USA in targeted populations is estimated to be 65 per cent and there are plans to increase this to 90 per cent in these groups. It is estimated that present levels of vaccination will reduce pneumococcal disease incidence in the elderly by 12 per cent and increasing the vaccine coverage could reduce this by as much as 25 per cent. Use of the 23-valent vaccine in the elderly is cost-effective.

Vaccination programs with 23vPPV in north Queensland and Victoria

Jeffrey Hanna reviewed the impact of the 23-valent polysaccharide vaccine on IPD in Far North Queensland. Over a seven year period, the incidence of IPD in Indigenous adults (eligible for vaccination at 50 years of age) has been reduced from 110 to 28 cases per 100,000 population.⁹ This rate is approximately the same as that seen in the non-Indigenous population. A vaccine effectiveness of 50 to 80 per cent has been estimated from these data.

Ross Andrews provided evidence of the impact of the 23-valent vaccine on IPD in Victoria. From the examination of IPD surveillance data and estimated 23vPPV coverage, it is estimated that the funded vaccine program for the elderly in Victoria has prevented 109 cases and 20 deaths since the program was started.

Impact of pneumococcal conjugate vaccine programs

In this session, there were presentations on the impact of 7vPCV from the sentinel surveillance sites in the USA and from three states with significant populations of Indigenous children living in rural and remote areas of northern Australia within the tropics (the Northern Territory, North Queensland and Western Australia). All these regions have demonstrated both significantly higher incidence and serotype diversity among Indigenous children.

Impact of 7vPCV on invasive pneumococcal disease in the United States of America

Cynthia Whitney presented exciting data on the impact of conjugate pneumococcal vaccines in the USA. The 7 valent conjugate vaccine was licensed for use in February 2000 and recommended for use in all children aged less than 2 years and in children aged between 2 and 4 years with risk factors for pneumococcal disease, from June 2000. In some states, vaccine is provided free of charge only to children who fulfil stringent means test requirements, while in other states, vaccine is provided free of charge to all children. Therefore vaccine coverage varies by area.

A comparison of age-specific rates of pneumococcal disease in 2001 in the USA with baseline levels in the pre-vaccine years, 1998-99, shows an overall decline of 69 per cent in the age group 0-12 months and a decline of 44 per cent in one to two-year-olds. Disease caused by vaccine serotypes has declined overall from 156 to 34 cases per 100,000 population and for vaccine serotype-related disease from 20 to 10 cases per 100,000 population. Disease caused by non-vaccine serotypes has increased from 12 to 16 cases per 100,000 population, but this change is not statistically significant. The decline in the incidence of vaccine serotypes range from 62 per cent for serotype 6B to 83 per cent for serotypes 14 and 19F. An interesting correlation between the declining incidence in children and an unexpected decline in adults has been observed - the first evidence of a herd effect of conjugate vaccines. There has been little change in the proportion of isolates resistant to penicillin seen following the introduction of 7vPCV, but to date there is also no evidence of serotype replacement in IPD cases.

Top of page

Impact of 7vPCV on invasive pneumococcal disease in northern Australia

Northern Territory

Christine Selvey, Director of Immunisation in the Northern Territory Centre of Disease Control, presented data on the impact of 7vPCV in the Northern Territory, adding to data presented the previous day. In the Northern Territory, 50 per cent of the annual birth cohort (all children born in Central Australia and Indigenous children in the rest of the Northern Territory) are eligible for the 7vPCV. Vaccination was implemented from 1 June 2001 (starting with those born after 1 April 2001) and the 'catch-up' program was initiated in September 2001. As at August 2002, 96 per cent of eligible children had received the first dose of vaccine at 2 months of age, 74 per cent of older children had started the 'catch-up' vaccine schedule and 64 per cent of these had completed the vaccine course. Only three mild to moderate adverse events after conjugate vaccination were recorded. A few cases of IPD in children who have received one or more doses of 7vPCV have occurred, mostly among the 'catch-up' group. It is still too early to evaluate the impact of the conjugate vaccine on IPD in the Northern Territory, given the expected small numbers of cases. In Central Australia, evaluation is complicated by the decrease in incidence of IPD among Aboriginal children aged under 2 years, from 1,500 cases per 100,000 population from 1994 to 1998, to 700 cases per 100,000 population from 1999 to 2001, prior to commencement of the 7vPCV program. No change was seen in the incidence of IPD among Aboriginal children in the Top End.

Western Australia

Carolien Giele, epidemiologist in the Communicable Disease Control Branch of the Health Department of Western Australia, presented data on the coverage of 7vPCV and incidence of IPD among Aboriginal children in Western Australia. There was good correlation between data on doses distributed and doses reported to the ACIR, with estimated coverage being high in rural and remote areas and sub-optimal in the urban area of Perth and surrounds. The small numbers of IPD cases in Aboriginal children precluded conclusions about the significance of 3 cases to date in 2002 but 2 of the 3 cases were not serotypes included in 7vPCV. Presumptive antibiotic treatment before sample collection is likely to reduce the identification of IPD cases in the north of the state.

North Queensland

In north Queensland, the uptake of IPD vaccination in the eligible birth cohort is estimated to be 70 per cent for the first dose, 60 per cent for the second and 50 per cent for the third (within one month of the scheduled age). The number of IPD cases in Indigenous children aged less than 15 years has fallen from 15 cases in 1999 to 6 cases to the end of September 2002. None of the cases in 2002 were caused by vaccine serotypes, while the prevalence of non-vaccine serotypes has shown little change. There is some evidence that the incidence of IPD in non-Indigenous children, who are not eligible for funded vaccination, has also declined in the same period. This, together with data suggestive of a fall in incidence of IPD in Indigenous adults since the introduction of 7vPCV, may be an early indication of herd immunity from the reduction in pneumococcal colonisation among vaccine-eligible children.

Impact of 7vPCV on ear disease

Northern Territory

Amanda Leach, Senior Scientist with the Menzies School of Health Research and the Cooperative Research Centre for Aboriginal and Tropical Health in Darwin, presented background data from her team's previous research into ear disease among Aboriginal children in the Northern Territory. She also discussed research in progress to monitor the future impact of 7vPCV on ear disease in a number of areas of the Northern Territory. Rates of tympanic membrane perforation among Aboriginal people from previous published studies range from 5 to 37 per cent, with the World Health Organization nominating 4 per cent or higher as a 'massive public health problem'.¹⁰ The Prevention of Otitis Media with Prevenar and Training (PROMPT) study, funded by Wyeth-Lederle vaccines, has recruited 20 communities for follow-up, with many having perforation rates among children of more than 25 per cent. The Prevenar Immunisation for Otitis Media Reductions in the Tiwi Islands (PRIORiTI) is a longitudinal study in the Tiwi community, with data on pneumococcal colonisation extending back for almost 10 years. Early results suggest that pneumococcal colonisation has decreased overall, with a decrease in 7vPCV serotypes counterbalanced to some degree by an increase in other serotypes. Clinical implications are unclear, but there appears to be some decrease in tympanic membrane perforations compared with historical data. Close follow-up in both study cohorts will continue. Given the early onset of colonisation previously found in these populations, indirect impacts via decrease in colonisation in older contacts of young infants may turn out to be as important as individual vaccine response in reducing ear disease.

Sydney

Michael Watson, Microbiologist and Infectious Disease Physician at The Children's Hospital Westmead, presented early results of a baseline comparison of serotypes seen in pneumococcal isolates from swabs from ear discharge. The predominant serotypes were very different from those seen in IPD isolates from the same population, with a predominance of 19F, as opposed to serotype 14. This has potential implications for the impact of 7vPCV in non-Indigenous populations when funded vaccination at a population level is introduced.

Top of page

Summary and conclusions

In relation to surveillance, the predominant issue discussed was universal versus sentinel enhanced surveillance of IPD. In northern Australia, it will be important for enhanced surveillance to continue and to be as complete as possible. There are a number of reasons for this. First, the high incidence and high serotype diversity of IPD in Indigenous children in these areas has prompted the recommendation for boosters with 23vPPV to increase serotype coverage. This makes high quality, comprehensive surveillance essential for national policy. It is also important internationally as such as vaccine program has not been implemented anywhere else but is potentially applicable to other comparable populations. Secondly, the small absolute numbers of cases require data to be accumulated as comprehensively as possible.

In relation to vaccine issues, both 23vPPV and 7vPCV policy are important. There was strong support from the meeting for the recent recommendation from the Australian Technical Advisory Group on Immunisation that both 23vPPV (for those over 65 years) and 7vPCV (for those less than 2 years) be publicly funded as universal programs. With respect to the current programs, there were important issues for Aboriginal and Torres Strait Islander people for both 23vPPV and 7vPCV. For 23vPPV, research is required into both the utility and frequency of boosters in adults as well as any potential role for 7vPCV in adults. Improving the identification of Aboriginal and Torres Strait Islander children is important, especially in urban areas.

Top of page

References

1. Forrest JM, McIntyre PB, Burgess MA. Pneumococcal disease in Australia Commun Dis Intell 2000;24:89-92.

2. McIntyre P, Menzies R, Krause V, Selvey L, Hall R, Misrachi A, et al. Surveillance of pneumococcal disease in Australian states and territories Commun Dis Intell 2000;24:93-95.

3. Fagan RL, Hanna JN, Messer RD, Brookes DL, Murphy DM. The epidemiology of invasive pneumococcal disease in children in Far North Queensland J Paediatr Child Health 2001;37:571-575.

4. McIntyre PB, Gilmour RE, Gilbert GL, Kakakios AM, Mellis CM. Epidemiology of invasive pneumococcal disease in urban New South Wales, 1997-1999. Med J Aust 2000;173:S22-S26.

5. Roche P, Krause V. Invasive pneumococcal disease in Australia, 2001 Commun Dis Intell 2002;26:505-519.

6. Andrews RM and Lester RA. Improving pneumococcal vaccination coverage among older people in Victoria. Med J Aust 2000;173:S45-S47.

7. French N, Nakiyingi J, Carpenter LM, Lugada E, Watera C, Moi K, Moore M, et al. 23-valent pneumococcal polysaccharide vaccine in HIV-1 -infected Ugandan adults: double-blind, randomised and placebo controlled trial. Lancet 2000;355: 2106-2111.

8. Pierce AB and Hoy JF. Is the recommendation for pneumococcal vaccination of HIV patients evidence based? J Clin Virol 2001;22:255-261.

9. Hanna JN, Young DM, Brookes DL, Dostie BG, Murphy DM. The initial coverage and impact of the pneumococcal and influenza vaccination program for at-risk indigenous adults in Far North Queensland. Aust N Z J Public Health 2001;25:543-546

10. Leach AJ, Morris PS. Perspectives on infective ear disease in indigenous Australian children. J Paediatr Child Health 2001;37:529-530.

Top of page

Author affiliations

1. Surveillance and Epidemiology Section, Department of Health and Ageing, Canberra, Australian Capital Territory

2. National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, Sydney, New South Wales

Top of page

Appendix: Abstracts of presentations from states and territories on invasive pneumococcal disease surveillance in 2002

Invasive pneumococcal disease surveillance in the Australian Capital Territory

Louise Carter, Communicable Disease Control Section, Australian Capital Territory Department of Health and Community Care

Invasive pneumococcal disease (IPD) was listed as a notifiable infection under the Australian Capital Territory Public Health Act 1997 in September 1999. Public health legislation requires the condition to be notified to the Australian Capital Territory health department by hospitals, medical practitioners and pathology laboratories. The Australian Capital Territory has a passive system which relies on the assistance of hospital infection control practitioners to review medical records and in-patient notes for information on vaccination history and factors which may predispose people to the disease. Serotyping of isolates from the Australian Capital Territory is performed in batches and does provide some feedback on intervention activities pertaining to IPD being conducted locally.

The burden of IPD in the Australian Capital Territory is low (around 5 cases per 100,000 population per annum), however, information other than demographic details provided by the reporting laboratories are often missing and details regarding pneumococcal vaccines previously administered are rarely validated. This presentation supports a uniform national surveillance system for IPD, so that trends regarding the control of this condition and the impact of the National Childhood Pneumococcal Vaccination Program can be accurately monitored.

Top of page

Invasive pneumococcal disease New South Wales, 2002 - in the beginning

Robin Gilmour, NSW Health Department

Invasive pneumococcal disease became notifiable by all laboratories in New South Wales in 2001, and 2002 saw the commencement of enhanced surveillance for notified cases who were aged less than 5 years or 50 years or older. Surveillance of IPD in New South Wales is derived from three sources: the New South Wales Notifiable Disease Database; the New South Wales enhanced IPD surveillance database (for cases aged less than 5 years or 50 years or more); and typing and antibiotic sensitivity testing from the Children's Hospital at Westmead.

The overall incidence of IPD in New South Wales is 13.4 cases per 100,000 population for the nine-month period. From the enhanced data (n=497) children aged less than 2 years continue to have the highest rate of disease (98.5 cases per 100,000 population). Adults aged more than 65 years accounted for 68 per cent, adults aged more than 85 years have the next highest rate of disease (74.5 cases per 100,000 population). Bacteraemia is the most common infection in children and pneumonia is most common in adults. Meningitis is uncommon in both age groups (3 per cent in adults and 7 per cent in children). Underlying illness was reported in 16 per cent of children and 72 per cent in adults. There have been 3 deaths (1.6%) reported in children aged under 5 years and 73 (29.9%) deaths in adults. Only 9 cases were reported as being Aboriginal or/and Torres Strait Islander. Eighty-two per cent of isolates in the Greater Sydney Region have been serotyped for the period January to June 2002. Thirty-six possible vaccine failures were identified up to September 2002.

Top of page

Invasive pneumococcal disease in the Northern Territory 1 January to 30 September 2002. How do the numbers compare to the same period in 2001?

Heather Cook and Vicki Krause, Centre for Disease Control, NT Department of Health and Community Services, Darwin

Invasive pneumococcal disease enhanced data has been reported from the entire Northern Territory since 1994. Very high rates have been documented, specifically in the under two year old Indigenous population with higher rates in this age group in the Centre than in the Top End.

Looking at the first nine months of 2002 there were 49 cases of IPD notified in the Northern Territory compared to 78 cases for the same period in 2001. The greatest reduction was in Top End in Indigenous children under 2 years, dropping from six cases to one case, followed by a decrease of five to zero cases in the same age group for Central Australian non-Indigenous cases in 2001 to 2002, respectively. No change was seen in this same age group in Central Australian Indigenous cases with 4 cases in each year while the Top End non-Indigenous cases decreased from 6 to 3 cases in this age group, in 2001 to 2002, respectively.

A notable decrease was also seen in the overall 15-49 year population where Indigenous cases dropped from 31 to 19 cases and non-Indigenous cases reduced from 6 to 4 cases, in 2001 to 2002, respectively.

Males represented 57 per cent of cases in 2002 and 63 per cent in 2001.

Indigenous status is very well reported in the Northern Territory and 78 per cent of the IPD cases in 2002 (and 67% in 2001) were Indigenous while 27 per cent of the Northern Territory population is Indigenous.

Although slightly decreased, pneumonia continued to be the most common overall primary clinical presentation (67% of cases in 2002 compared to 78% in 2001). In those 15 years and older, 83 per cent of all cases in 2002 presented as pneumonia. The only two cases of meningitis in 2002 occurred in non-Indigenous adults between 15 and 49 years of age.

Three IPD deaths occurred in 2002 with two of these occurring in the Indigenous 15-49 year age range, a case fatality rate of 11 per cent for this age group, and an overall rate of 6 per cent while the overall rate was 3 per cent in 2001.

Serotyping results were available for 92 per cent of the cases from 2002 with 71 per cent of the isolates tested in the under 2 year age group being those found in the 7-valent vaccine and all isolates in this age group were those found in the 23-valent vaccine. For those 2 years and over, 87 per cent of the isolates were covered by the 23-valent vaccine. This figure compares to 76 per cent in 2001.

In 2002, 5 cases of 23-valent vaccine serotype IPD occurred in fully vaccinated persons 5 years of age and older with each having one or more recognised risk factors for IPD as did the 7 same-category cases in 2001. Cases of IPD in children who received the 7-valent vaccine is discussed elsewhere.

Top of page

Invasive pneumococcal disease trends in Queensland 1997-2002: fact or artefact?

Dr Robyn Pugh, Senior Epidemiologist, Communicable Diseases Unit, Queensland Department of Health

Invasive pneumococcal disease was made a notifiable disease in Queensland in 1996 and enhanced surveillance of cases aged under 5 years began state-wide in July 2001. However, IPD surveillance began in Far North Queensland in 1992 with comprehensive enhanced surveillance data collection on all cases since 1999.

Annual rates

Annual IPD rates increased from 1997 to 2000. There were 11.9 notifications per 100,000 population in 2001 which was slightly lower than in 2000. The highest rates occurred in children aged under 2 years (peaking in 2000 at 133 notifications per 100,000 population) followed by rates for persons aged 75 years or over. Fifty-six per cent of cases were males. In the 9 months to 30 September 2002, there were 351 notifications compared with 343 notifications in same period in 2001. The age distribution of these cases in 2002 was children aged under 5 years (38 per cent, including 26 per cent under 2 years), 5-14 years (5 per cent), 15-49 years (26 per cent) and 50 years or over (32 per cent). The age and gender profile has been similar each year since 1997.

Data collection

Data collection has improved since 1997 especially with the commencement of enhanced surveillance but records are still incomplete, e.g. no Indigenous status was recorded for 56 per cent of cases (29 per cent of cases aged under 5 years) in 2002 to date. There remains an over-representation of cases who are indigenous, with 10 per cent of notified cases aged under 5 years (13 per cent of under 2-year-olds) recorded as Indigenous.

Statistical Divisions in north Queensland

Statistical Divisions in north Queensland had the highest rates of IPD between 1997 and 2001; peak rates occurred in 2000 with 20.8 notifications per 100,000 population in the Far North and 24.0 notifications per 100,000 population in the Northern Statistical Division. The notification rates in divisions are similar this year compared with the same 9 month period in 2001 with some notable exceptions. The rates in the Far North and Northern divisions have fallen and are similar to the rate in Brisbane.

Clinical presentation

Clinical presentation of cases aged under 5 years during this year was similar to the same period last year. The majority presented with a bacteraemia (59 per cent) and 32 per cent presented with pneumonia. Only 1.6 per cent of cases presented solely with meningitis.

Death rate

The reported death rate for notified cases was 1.1 per cent for this 5-year period, slightly higher in the earlier years for under 5-year-olds. There has been 4 deaths this year to date, compared with 6 deaths in the same period last year.

Overall, the most common serotype in 2002 to date is serotype 14 but this varied depending on age and Indigenous status of the cases.

Prevenar coverage rate

The Prevenar coverage rate for Indigenous children aged under one year (i.e., for those born after the commencement of the July 2001 schedule) is 58 per cent (fully vaccinated) and 14 per cent (partially vaccinated). The fully vaccinated rates varied from 69 per cent in northern Queensland to 45 per cent in central and 36 per cent in south Queensland. The coverage rates depended on the service provider. Table 1 shows the range of vaccination coverage rates.

Table 1. Prevenar coverage rate for Indigenous children aged under 1 year, Queensland, post July 2001 immunisation schedule, by service provider

Service provider	Fully vaccinated* %	Partially vaccinated* %
Aboriginal Health Service	76	21
Child health/community health services	82	12
Councils	55	23
Hospitals	50	13
Medical practices	32	12

The Pneumovax program for Indigenous adults aged 50 years or over began in north Queensland in 1995 and other areas in Queensland in 1997; the overall coverage up to 30 June 2002 is 53 per cent.

Fact or artefact?

The increase in notifications from 1997 to 2000 may be due to improved surveillance and awareness of this disease. The slight fall in rates in 2001 was chiefly due to the drop in rates for children aged under 2 years. Errors in estimating coverage rates may be due to duplicate records, inaccurate Indigenous identification, inaccurate records and/or incorrect population estimates. It may be too soon to assess the effectiveness of the vaccination strategy and ascertainment of cases may still be improving.

Top of page

Enhanced surveillance of invasive pneumococcal disease in South Australia, 2002

Sharon Hart, Public Health Nurse, Communicable Disease Control Branch, South Australian Department of Human Services

Enhanced surveillance of invasive pneumococcal disease of cases in all age groups was commenced in South Australia in 2001. The total number of notified cases for 2001 was 118 cases. The dataset for 2001 is not complete, as IPD did not become notifiable in South Australia until January 2002. Data are obtained from a range of sources, including the referring doctor, infection control practitioners and hospital medical records.

The total number of cases from 1 January to 30 September 2002 was 129 cases. Of these, 101 (78.3 per cent) have been serogrouped. Of the remaining cases, 19 (14.7%) are waiting to be serogrouped, 3 (2.4%) isolates were non-viable and 6 (4.7%) were discarded by the primary laboratory. Continuous Quality Improvement activities have been developed to improve the completeness of the dataset.

Half the 2002 cases were female, 53 (41%) were aged under 5 years [36 (28%) aged under 2 years], 11 (8.6%) aged 5-14 years, 21 (16.4%) aged 15-49 years, and 44 (34%) aged over 50 years (31 (24%) aged 65 years or over).

There were 4 (3.1%) indigenous cases, one case aged 2-4 years, one case aged 5-14 years, two cases aged 15-49 years, and there were no indigenous cases aged over 50 years. Both of the cases aged 15-49 years had chronic illness but had not been immunised. Indigenous status is unknown for only one case (<1%) in 2002 compared to 24 cases (20.3%) in 2001.

Of the 36 cases aged under 2 years, 31 (86%) have no other identified risk factors. In the cases aged 2-4 years, 14 of the 17 cases (82.3%) have no other identified risk factors. However, in the cases aged 65 years and over, 25 (80.6%) had identified risk factors.

There have been 7 reported deaths for the year to date. There were no reported deaths in indigenous cases.

In the four cases aged 65 years or over, one case had been vaccinated, one case was not vaccinated and for two cases, vaccination status could not be determined.

Of the 53 cases aged under 5 years, 40 (75.5%) presented with a clinical bacteraemia, 6 (11.3%) presented with pneumonia and 4 (7.5%) presented with meningitis. In the 31 cases aged 65 years or over, 25 (80.6%) presented with pneumonia.

There were 7 cases of invasive pneumococcal disease in vaccinated individuals. Of these, 5 cases were serogroup 14, one was serogroup 9V (with intermediate resistance to penicillin) and one has not been serogrouped to date.

Top of page

Invasive pneumococcal disease in Tasmania: work in progress

David Coleman, Communicable Disease Surveillance, Health and Human Services, Hobart

History

Invasive pneumococcal disease was made notifiable on 30 September 2000. All initial notifications are made by five laboratories, two of which are in public hospitals and three are private. This gives state-wide coverage of all age groups in the 470,000 population. Pneumococcal surveillance is partly incorporated in general surveillance activities which involves two full time staff.

Case definition

Case definition depends on identification of a culture-positive isolate from a sterile site. There is no local PCR available. Serotyping is done at the Microbiological Diagnostic Unit in Melbourne.

Review of individual hospital records identified 76 paediatric cases between 1994 and 2000. In 1998, 2.6 per cent (2 isolates) showed intermediate penicillin sensitivity; all were fully sensitive to third generation cephalosporins. No serotyping was available. The incidence was 28.5 cases per 100,000 population aged under five years and 54.3 cases per 100,000 population aged under 2 years.

Thirty-four per cent of cases had risk factors, and there were 2 deaths.¹

Surveillance process

The surveillance process involves receipt of laboratory reports, sending a questionnaire to the hospital seeking clinical information and the name of the patient's GP, followed by a questionnaire to the GP. In 2001 (retrospective from the middle of the year) 95 per cent of cases had hospital questionnaires, 44 per cent had GP questionnaires, and 65 per cent of the isolates were typed. By late 2002, 90 per cent of cases had hospital data (our aim is 100%); 48 per cent had GP data (aim is 95%); and typing was done or was pending in 94 per cent of cases.

Summary of cases in 2002 (to end September)

There were 52 cases of invasive pneumococcal disease notified in 2002 up to the end of September, (compared with 42 for same period in 2001) (Table 2). Twelve of the 15 cases aged 0-4 years were under 2 years of age (23% of total). Seventy-seven per cent of all cases were male: 14 of the 15 paediatric cases (93%) were male. Eight of 52 cases died (6 of the 8 deaths had risk factors). One unvaccinated child died of meningitis: this child had no risk factors. One isolate showed reduced sensitivity to penicillin and cephalosporins. Four men aged 58 to 80 years with risk to factors (respiratory/cardiac, renal, or malignant disease) had been vaccinated between 1997 and 2001; serotyping was pending. One boy may have had two episodes of infection: pneumococcal meningitis (serotype 19F) at 11 months; and pneumococcal bacteraemia at 16 months. Another boy who had received three doses of vaccine developed bacteraemia (serotype 6B) at three years of age.

Table 2. Summary of invasive pneumococcal disease cases, Tasmania, 1 January to 30 September 2002, by age

Age (years)	Cases n (%)
0-4 <2	15 (28) 12 (23)
5-14	0 (-)
5-49	13 (25)
50+	24 (47)
Total	52

The Tasmanian paediatric pneumococcal vaccination program commenced in 2001, with a target Indigenous population of 745 persons. The Pneumovax Indigenous program targets adults over 50 years, and persons aged 15 years or over, who have risk factors.

Reference

1. Christie DJ, Coleman DJ, Wan X, Jacobs MA, Carapetis JR. Childhood invasive pneumococcal disease in Tasmania, 1994-2000. J Paediatr Child Health 2002;38:445-449.

Top of page

Invasive pneumococcal disease surveillance in Victoria

Catherine Ferreira, Megan Counahan and Ross Andrews, Communicable Diseases Section, Department of Human Services, Victoria

Since May 2001, medical practitioners and laboratories have been required to notify the Department of Human Services, Victoria, of all cases of invasive pneumococcal disease. This report covers notification data for the 12 month period from 1 October 2001 to 30 September 2002. There were 449 notifications, 53 per cent were male, less than one per cent were identified as indigenous and there were 21 deaths (case fatality rate: 4.7%). The highest notification rate was among infants (68 cases per 100,000 population of children aged under 2 years).

Serotype information was available for 79 per cent (n=354) of cases. Among infants aged under 2 years, 89 per cent (57 of 64) of the serotypes isolated were either in or related to the 7-valent vaccine while for persons aged 2 years or over years, 98 per cent (284 of 290) were in or related to the 23-valent vaccine.

Pneumococcal vaccine for persons aged 65 years or over has been publicly funded in Victoria since 1998. Data on vaccine failures for cases detected from 1 January 2001 (prior to IPD becoming notifiable) up to 30 September 2002 were reviewed. Twenty-six vaccinated people developed IPD: one was a partially vaccinated infant who had received the 7-valent conjugate vaccine, the remainder had received the 23-valent polysaccharide vaccine. Less than one per cent of cases aged 2-64 years were vaccine failures while 16 per cent of those aged 65 years or over were vaccine failures. The high proportion of vaccine failures in the older age group is consistent with much higher vaccine coverage in this group.

Top of page

Enhanced surveillance of invasive pneumococcal disease in Western Australia, 1 January to 30 September, 2002

Carolien Giele, Communicable Disease Control Branch, Department of Health, Western Australia.

Enhanced surveillance of invasive pneumococcal disease has been undertaken by the Vaccine Impact Surveillance Network for all age groups in Western Australia since 1996. IPD became notifiable in 2001, and since that time the Department of Health and the Vaccine Impact Surveillance Network have collaborated in data collection. After doctors or laboratories report IPD cases, demographic and clinical information is collected from managing physicians and/or by reviewing case notes.

During the nine-month period from January to September 2002, there were 159 IPD notifications, comprising 91 males and 68 females (notification rate: 11 cases per 100,000 population per year). The majority of cases occurred in three age groups: children under 5 years (n=55, 35%), adults aged 15-49 years (n=37, 23 per cent), and adults over 65 years (n=34, 21%). Notification rates were higher for Indigenous people compared to non-Indigenous people across all age groups. Incidence was highest in children aged under 2 years which was three times higher in Indigenous children (267 cases per 100,000 population per year) compared to non-Indigenous children (90 cases per 100,000 population per year). Of the 121 (76%) cases with ethnicity data, 21 (17 per cent) were Indigenous. There were 12 deaths (case fatality rate: 7 per cent), including 2 deaths in non-Indigenous children aged under 2 years.

Serotype and antibiotic susceptibility data were available for 139 (87 per cent) and 156 (98 per cent) IPD isolates, respectively. Of the 32 isolates from cases aged under 2 years, 78 per cent of serotypes were contained in the 7-valent conjugate vaccine. Of 107 isolates from cases aged 2 years or over, 86 per cent of serotypes were contained in the 23-valent polysaccharide vaccine. Twelve per cent (n=18) of isolates showed reduced susceptibility to penicillin.

These data show that available pneumococcal conjugate and polysaccharide vaccines provide good coverage for strains causing invasive disease in Western Australia. In this State provision of conjugate pneumococcal vaccine to all children as part of the funded childhood immunisation schedule would have considerably greater effect than the meningococcal serogroup C vaccine.


This article was published in Communicable Diseases Intelligence Volume 27, No 1, March 2003.