This article {extract} was published in Communicable Diseases Intelligence Vol 29 No 1 March 2005 and may be downloaded as a full version PDF from the Table of contents page.
Results, continued
Vaccine preventable diseases
This section summarises the national notification data for laboratory-confirmed influenza and diseases targeted by the standard childhood vaccination schedule in 2002. This includes diphtheria, Haemophilus influenzae type b infection, measles, mumps, pertussis, invasive pneumococcal disease, poliomyelitis, rubella and tetanus. There were no changes to the Australian Standard Vaccination Schedule in 2002.
There were 11,711 notifications of vaccine preventable diseases (VPDs) with onset dates in 2002; 11.6 per cent of the total notifications to NNDSS. Pertussis was the most commonly notified VPD (5,388 cases or 46% of all VPD notifications). Numbers of notifications and notification rates for vaccine preventable diseases in Australia are shown in Tables 2 and 3.
Diphtheria
There were no cases of diphtheria reported in 2002. A single case of cutaneous diphtheria in 2001 was the first case reported since 1993.14
Haemophilus influenzae type b disease
Notifications of Haemophilus influenzae type b (Hib) have fallen more than 30-fold since 1991 due to the impact of Hib conjugate vaccines.15
There were 29 notifications of Hib disease in 2002, a rate of 0.1 cases per 100,000 population. This is a similar rate to that reported in 2001, when the lowest number of notifications was recorded since national surveillance began in 1991. Twelve cases (41% of total cases) were in children aged less than five years of age and six were infants aged less than one year (Figure 37). There continued to be more cases reported in females than males, (male:female ratio 0.7:1) in 2002. The Northern Territory had the highest notification rate (1.5 per 100,000 population, three cases) although most cases (10/29, 34%) were from New South Wales. Of the 24 cases with a known Indigenous status, 11 were Indigenous and 13 were non-Indigenous. Nine of the cases in Indigenous people occurred in children aged less than 5 years (17 cases per 100,000 population) compared with 3 cases in non-Indigenous children (0.2 cases per 100,000 population). Although there has been a significant decline in Hib disease, Indigenous children make up a greater proportion of cases than in the pre-immunisation era.15
Figure 37. Notification rate of Haemophilus influenzae type b infection, Australia, 2002, by age group and sex
Laboratory-confirmed influenza
There were 3,665 reports of laboratory-confirmed influenza in 2002, a rate of 18.6 cases per 100,000 population. In 2002, data were available from all jurisdictions for the full year, in contrast to 2001, when reporting was incomplete. Notifications of influenza showed a peak in August (late winter) (Figure 38).
Figure 38. Notifications of laboratory-confirmed influenza, Australia, 2002 by month of onset
The highest rates of influenza were in children aged less than 5 years (Figure 39). This may reflect not only the high incidence of influenza in children, but also that children are more likely to undergo virological testing for respiratory viruses on presentation to hospital. The male to female ratio was 1.2:1.
Figure 39. Notification rate of laboratory-confirmed influenza, Australia, 2002, by age group and sex
In 2002, influenza A was the dominant type, 99 per cent of which were subtype H3N2 with only a single H1N2 isolate. The influenza A (H3N2) isolates analysed were closely related to the vaccine strains A/Moscow/10/99 and the A/Panama/2007/99. Influenza B accounted for 21 per cent of all isolates and most of these were of the B/Victoria lineage, which has not been seen in Australia for a decade. This strain had a haemagglutinin closely related to the B/HongKong/330/2001 reference strain and a neuraminidase similar to the B/Sichuan/379/99-like viruses, indicating that a genetic reassortment event had occurred. These new B/Hong Kong/330/2001-like viruses were associated with two outbreaks in school groups.16 Although the 2002 influenza vaccine was not directed against the new strain, a proportion of asymptomatic vaccinees who had received the 2002 influenza vaccine showed protective antibody titres.16 In 2002, 77 per cent of the over 65 year age group in Australia received influenza vaccination.17
Measles
There were 31 confirmed measles cases in 2002, a national rate of 0.2 cases per 100,000 population. This is a steep decline in numbers compared with 2001 when 141 cases were notified, and is the lowest annual rate for Australia since national surveillance began in 1991 (Figure 40). The highest rate was in Victoria with 0.3 cases per 100,000 population (14 cases) (Tables 1 and 2).
Figure 40. Notification rate of measles, Australia, 1996 to 2002, by month of onset
All age groups had the lowest rates on record in 2002. Rates were highest in the 0-4 year age group (0.6 cases per 100,000 population), followed by the 20-24 year age group (0.5 cases per 100,000 population) and the 15-19 year age group (0.4 cases per 100,000 population). Of the eight cases in the under 5 year age group two were aged less than one year. There was only a single case reported in each of the 5-9 and 10-14 year age groups. This illustrates the ongoing impact of the Measles Control Campaign (which involved the mass vaccination of primary school aged children in 1998) and lowering the age for the second dose of measles, mumps, rubella vaccine to age four years. As a result of improved immunity in children and a residual cohort of susceptible adults born in the late 1970s and early 1980s, the proportion of cases in young adults has increased since 1998. In 2002, 35 per cent of the reported cases were aged 20-29 years, where as between 1993 and 1998 only 8 per cent of cases were in this age range.
Of the 31 cases reported in 2002, nine were recorded as having acquired their infection outside Australia. The vaccination status was recorded for 21 cases: two were fully vaccinated for age and 19 were unvaccinated. There were a number of outbreaks of measles in Australia in 2002. In Victoria in May and June a cluster of measles in three young adults was identified. The cases were unvaccinated and had no recent history of travel. In New South Wales in the second quarter of 2002 there were two linked cases of measles. The first was an unvaccinated 1-year-old child who had recently travelled in Pakistan and the second, a vaccinated 1-year-old child contact. An outbreak in the Whitsunday region of north Queensland occurred in July and August 2002 in unvaccinated children with exposure to an infected overseas traveller. Secondary cases occurred in New South Wales as well. This outbreak had two generations of transmission and resulted in a total of seven cases from four families.18
Mumps
In 2002, there were 69 notifications of mumps, a rate of 0.4 cases per 100,000 population. This is a decrease of 39 per cent on the 114 cases reported in 2001 and the lowest rate since all states and territories began notifying the disease in 1996. There were notifications from all age groups under 75 years (Figure 41) with the majority (n=48, 70%) from people aged 15 years or more. The highest notification rate (0.6 cases per 100,000 population) was in the 0-4 year age group. As in most years, there was a preponderance of cases in males (male: female ratio 1.5:1).
Figure 41. Notification rate for mumps, Australia 2002, by age group and sex
Pertussis
Pertussis continues to be the most common vaccine preventable illness in Australia, with periodic epidemics occurring at intervals of three to five years on a background of endemic circulation (Figure 42).19 In 2002, there were 5,388 cases notified (27.4 cases per 100,000 population), a 43 per cent decrease on the epidemic year of 2001 when 9,515 cases were notified.
Figure 42. Notifications of pertussis, Australia, 1991 to 2002, by month of onset
The highest notification rates were among children aged less than one year (117.4 cases per 100,000 population) and those aged 10-14 years (85.3 cases per 100,000 population) (Figures 43 and 44). The notification rate in children aged less than one year exceeded that for the 10-14 year age group for the first time since 1998 (Figure 43). This may reflect the impact of the fifth dose of the pertussis vaccine, given to 4-year-olds since 1994, and the resultant cohort effect. The overall male to female ratio was 0.9:1.
Figure 43. Notification rates for pertussis, Australia, 1996 to 2002, by age group
Figure 44. Notification rates for pertussis, Australia, 2002, by age group and sex
Notification rates of pertussis varied considerably by geographic location (Map 6). The highest rate was in Queensland (50 cases per 100,000 population) and the lowest rate was in Tasmania (8.7 cases per 100,000 population).
Map 6. Notification rates of pertussis, Australia, 2002, by Statistical Division of residence
Pneumococcal disease (invasive)
There were 2,271 notifications of invasive pneumococcal disease (IPD) in Australia in 2002 giving a rate of 11.5 cases per 100,000 population. While the largest numbers of cases were reported from New South Wales, Queensland and Victoria (Table 1), the highest rate was in the Northern Territory (32.8 cases per 100,000 population). The geographical distribution of IPD varied within states and territories, with the highest rates in Central and northern Australia.
IPD was largely a disease of the very young and very old. The highest rates of disease were among children aged less than 5 years (56.8 cases per 100,000 population) and adults aged more than 85 years (51.7 cases per 100,000 population) (Figure 45). There were more cases among males, with a male to female ratio of 1.3:1. IPD notifications peaked in late winter and early spring with the largest number of notifications in August.
Figure 45. Notification rate for invasive pneumococcal disease, Australia, 2002, by age and sex
Additional data were collected on cases of invasive pneumococcal disease in all Australian jurisdictions during 2002. Analyses of these data have recently been published.21
Poliomyelitis
No cases of poliomyelitis were reported in Australia in 2002.
There were 46 cases of acute flaccid paralysis reported in 2002. Of these, 33 occurred in children aged less than 15 years of age; this represents 83 per cent of the WHO indicator target for acute flaccid paralysis. Testing of faecal specimens identified poliovirus Sabin vaccine-like type 3 in a single acute flaccid paralysis case, who was fully vaccinated. The conclusion of the expert review committee was that this was an incidental finding in a case of acute focal neuropathy.22
Rubella
In 2002, there were 254 notifications of rubella, a notification rate of 1.3 cases per 100,000 population. This rate is slightly lower than in 2001 (1.4 cases per 100,000 population) and is the lowest rate recorded since national reporting of rubella commenced (Figure 46).
Figure 46. Notifications of rubella, Australia, 1996 to 2002, by month of onset
As in the past two years, notification rates were highest in males aged 20-24 years (12.9 cases per 100,000 population) (Figure 47). The male to female ratio of notified cases has been increasing since 1999 due to this residual cohort of susceptible young adult males and improved childhood immunity. In 2002 the male:female ratio was 3:1.
Figure 47. Notification rate for rubella, Australia, 2002, by age and sex
In contrast to the rest of Australia, rates of rubella in Queensland have been increasing since 2000, especially amongst young adult males aged 15-29 years and females aged 15-24 years. In 2002, Queensland accounted for 75 per cent of all notified cases of rubella (notification rate 5.1 cases per 100,000 population).
There were 56 cases of rubella notified from women of childbearing age (15-49 years) in 2002, eight more than in 2001 when the lowest number on record was reported. A single notification of congenital rubella was received in 2002, which occurred in a child infected outside Australia (Australian Paediatric Surveillance Unit report, 2002). Ongoing transmission in Queensland has resulted in two locally acquired cases of congenital rubella syndrome in 2003.23,24,25
Tetanus
Since 1995, less than 8 cases of tetanus have been notified each year. In 2002, there were three reported cases (two female, one male). All three cases were adults aged 64 years or above. This is consistent with the age distribution of notifications in recent years, and indicates that tetanus has become a disease of older adults.
Childhood vaccination coverage reports
Estimates of vaccination coverage both overall and for individual vaccines for children at 12 months, 24 months and 6 years of age in 2002 are shown in Tables 9, 10 and 11 respectively.
Table 9. Percentage of Australian children born in 2001 vaccinated according to data available on the Australian Childhood Immunisation Register, estimate at one year of age
Vaccine |
Birth date | |||
|---|---|---|---|---|
| 1 Jan–31 Mar 2001 | 1 Apr–30 Jun 2001 | 1 Jul–30 Sep 2001 | 1 Oct–31 Dec 2001 | |
| Diphtheria, tetanus, pertussis (%) | 91.8 |
92.5 |
92.7 |
92.6 |
| Poliomyelitis (%) | 91.7 |
92.4 |
92.6 |
92.5 |
| Haemophilus influenzae type b (%) | 93.7 |
94.7 |
94.9 |
94.7 |
| Hepatitis B (%) | 94.0 |
94.9 |
95.1 |
95.0 |
| Fully vaccinated (%) | 90.2 |
91.2 |
91.7 |
91.4 |
Table 10. Percentage of Australian children born in 2000 vaccinated according to data available on the Australian Childhood Immunisation Register, estimate at two years of age
Vaccine |
Birth date | |||
|---|---|---|---|---|
| 1 Jan–31 Mar 2000 | 1 Apr–30 Jun 2000 | 1 Jul–30 Sep 2000 | 1 Oct–31 Dec 2000 | |
| Diphtheria, tetanus, pertussis (%) | 90.3 |
90.9 |
91.4 |
91.2 |
| Poliomyelitis (%) | 94.2 |
94.7 |
94.8 |
94.9 |
| Haemophilus influenzae type b (%) | 95.0 |
94.3 |
94.0 |
94.0 |
| Measles, mumps, rubella (%) | 93.2 |
93.8 |
94.2 |
94.2 |
| Fully vaccinated (%) | 88.1 |
88.8 |
89.4 |
89.0 |
Table 11. Percentage of Australian children born in 1996 vaccinated according to data available on the Australian Childhood Immunisation Register, estimate at six years of age
Vaccine |
Birth date | |||
|---|---|---|---|---|
| 1 Jan–31 Mar 1996 | 1 Apr–30 Jun 1996 | 1 Jul–30 Sep 1996 | 1 Oct–31 Dec 1996 | |
| Diphtheria, tetanus, pertussis (%) | 83.7 |
84.1 |
84.5 |
84.3 |
| Poliomyelitis (%) | 84.0 |
84.4 |
84.7 |
84.5 |
| Measles, mumps, rubella (%) | 82.4 |
83.1 |
83.7 |
83.6 |
| Fully vaccinated (%) | 80.6 |
81.4 |
82.2 |
82.2 |
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This issue - Vol 28 No 1, March 2004
NNDSS Annual report 2003
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