Megge Miller, Paul Roche, Keflemariam Yohannes, Jenean Spencer, Mark Bartlett, Julia Brotherton, Jenny Hutchinson, Martyn Kirk, Ann McDonald, Claire Vadjic

Results - Vaccine preventable diseases

This section summarises the national notification data for influenza and diseases targeted by the Australian Standard Vaccination Schedule (ASVS) in 2003. These include diphtheria, Haemophilus influenzae type b infection, measles, mumps, pertussis, invasive pneumococcal disease, poliomyelitis, rubella and tetanus. (Notifications for hepatitis B and meningococcal disease, which are also targeted by the ASVS, can be found in this report under ‘Bloodborne diseases’ and ‘Other bacterial infections.’ Varicella-zoster infection is not a nationally notifiable disease.)

A number of changes to the Australian Standard Vaccination Schedule occurred during the time period of this report. Firstly, meningococcal C conjugate vaccine was funded for all children aged 1–18 years in 2003, with a routine dose incorporated into the ASVS at 12 months of age and a catch-up program for older ages (implementation of which varied by jurisdiction). Secondly, in September 2003, the National Health and Medical Research Council (NHMRC) endorsed the recommended changes to the ASVS. Two new vaccines were added to the ASVS – conjugate pneumococcal vaccine at 2, 4 and 6 months of age and varicella (chickenpox) vaccine at 18 months of age. Neither of these recommended vaccines was funded for the National Immunisation Program (NIP) in 2003.

The NHMRC also endorsed two further modifications to the ASVS. Firstly, inactivated poliomyelitis vaccine was recommended to replace oral polio vaccine (OPV) at 2, 4 and 6 months and at 4 years of age, due to the extremely rare but real risk of vaccine associated paralysis with OPV. However, OPV was recognised as being an acceptable alternative and remained on the NIP in 2003. Secondly, the timing of the pertussis vaccination schedule was changed by the removal of the 18 month booster and the addition of a booster at 15–17 years of age, resulting in a new schedule of administration at 2,4, 6 months, 4 years and 15–17 years. Removal of the 18 month dose was implemented immediately from September 2003, with the dose at 15–17 years replacing diphtheria-tetanus vaccine in the NIP from January 2004. The dose at 18 months was removed due to evidence suggesting that the primary schedule provides protection for at least 6 years and the emerging problem of local reactions to the fourth dose at 18 months.⁸

There were 11,113 notifications of vaccine preventable diseases (VPDs) with onset dates in 2003; 10.6 per cent of the total notifications to NNDSS. Pertussis was the most commonly notified Vaccine Preventable Disease (5,106 cases or 46% of all VPD notifications). Numbers of notifications and notification rates for VPDs in Australia are shown in Tables 2 and 3.

Diphtheria

There were no cases of diphtheria reported in 2003. A single case of cutaneous diphtheria in 2001 was the first case reported since 1993.⁹

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. 5 There were 19 notifications of Hib disease in 2003, a rate of 0.1 case per 100,000 population. This is 10 (35%) fewer cases than reported in 2002, and is the lowest number of notifications recorded since national surveillance began in 1991. Ten cases (53% of the total ) were in children aged less than 5 years and four were infants aged less than one year (Figure 36). There were nine cases in males and 10 cases in females, (male:female ratio 0.9:1).

Figure 36. Notification rate of Haemophilus influenzae type b infection, Australia, 2003, by age group and sex

The Northern Territory had the highest notification rate (1.0 per 100,000 population, 2 cases) although most cases were from New South Wales (n=6) and Queensland (n=5).

Of the 11 cases with a known Indigenous status, three were Indigenous and eight were non-Indigenous. Two of the three Indigenous cases occurred in children aged less than 5 years, compared with one of the eight cases in non-Indigenous people. Following the significant overall decline in Hib disease, Indigenous children now make up a greater proportion of cases than in the pre-immunisation era.⁵

The vaccination status of 11 of 19 cases was known – seven were unvaccinated, two were partially vaccinated and two were fully vaccinated.

Influenza (laboratory confirmed)

There were 3,587 reports of laboratory-confirmed influenza in 2003, a rate of 18 cases per 100,000 population. Notifications of influenza showed a peak in August (late winter, Figure 37).

Figure 37. Notifications of laboratory-confirmed influenza, Australia, 2003, by month of onset

Children aged less than 5 years made up 48 per cent of all notifications and had the highest rates of disease (136.6 cases per 100,000 population, Figure 38). 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 38. Notification rate of laboratory-confirmed influenza, Australia, 2003, by age group and sex

In 2003, 94 per cent of circulating viruses were influenza A. Of isolates analysed, 938 were A(h4), two were A(h2) strains and five were influenza B. The majority (98%) of A(h4) viruses were A/Fujian/411/2002 (h4N2)-like with significant antigenic drift. The 2003 Australian influenza vaccine strain, which contained the A/Panama/2007/99 virus, induced two to fourfold lower antibody responses to the Fujian strain. In 2003, 77 per cent of those aged 65 years or over in Australia received influenza vaccination.⁶

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Measles

There were 92 confirmed measles cases in 2003, a national rate of 0.5 cases per 100,000 population. This is a threefold increase compared with 2002 when only 31 cases were notified, but is still the second lowest annual rate for Australia since national surveillance began in 1991 (Figure 39). The highest rate was in South Australia with 1.6 cases per 100,000 population (24 cases), where most cases were attributable to a single outbreak. In 2003, there were no cases reported from the Australian Capital Territory, Tasmania or Western Australia, and only a single case reported from the Northern Territory—the first case from this jurisdiction since 1999 (Tables 1 and 2).

Figure 39. Notifications of measles including major outbreaks, Australia, 1997 to 2003, by month of onset

Rates were highest in the 20–24 year age group (1.7 cases per 100,000 population), followed by the 0–4 year age group (1.3 cases per 100,000 population) and the 25–29 year age group (1.3 cases per 100,000 population; Figure 40). Of the 16 cases in the under 5 year age group, seven were aged less than one year.

Figure 40. Notification rate of measles, Australia, 2003, by age group and sex

Of the 92 cases reported in 2003, 75 (81%) occurred in seven outbreaks in four States (Table 12). The index case in five of the seven outbreaks acquired their infection outside Australia.

Table 12. Outbreaks and clusters of measles, Australia, 2003*

Jurisdiction	Month of onset	Number of linked cases (including index case)	Place of acquisition of infection in index case
NSW	June	8	Overseas
Qld	Jan–Feb	4	Australia
	Aug–Oct	5	Overseas
SA	May	2	Overseas
	Aug–Oct	21	Overseas
Vic	Feb	20	Unknown
	Apr	15	Overseas

* There were no measles cases reported in 2003 from the Australian Capital Territory, Tasmania or Western Australia and only a single case reported from the Northern Territory.

The vaccination status was recorded for 30 cases: none were fully vaccinated for age, 13 were partially vaccinated and 17 were unvaccinated.

Studies of measles virus circulating in Australia between 1999 and 2001 provide evidence of the absence of a strain indigenous to Australia and the reintroduction of measles virus mainly from South East Asia causing limited outbreaks in susceptible populations in Australia.¹⁰

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Mumps

In 2003, there were 76 notifications of mumps, a rate of 0.4 cases per 100,000 population. This is a 10 per cent increase on the 69 cases reported in 2002, but is still the second lowest rate since all states and territories began notifying the disease in 1996.

Compared with 2002, most of the increase in 2003 was in adult age groups, specifically the 20–24, 35–39 and 40–44 year age groups. The rate for the 0–4 year age group (0.7 cases per 100,000 population; Figure 41) was similar to that seen in 2002, when it was the lowest on record. Rates in the 5–19 year age group continued to decline to new record lows in 2003. This is presumably due to the ongoing impact of the Measles Control Campaign (which targeted primary school aged children with the MMR vaccine in 1998) and coverage with a two-dose schedule prior to school entry. As in previous years, there was a preponderance of cases in males (male: female ratio 1.5:1).

Figure 41. Notification rate for mumps, Australia, 2003, by age group and sex

A study of mumps and rubella notifications in Victoria concluded that there was a low positive predictive value of clinical diagnoses for these infections and that notification rates in 2001–02 in Victoria for mumps were an over-estimate of the number of true cases.¹¹ New national surveillance case definitions for NNDSS, introduced in January 2004, will exclude clinical diagnoses of mumps without laboratory confirmation or a confirmed epidemiological link.

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Pertussis

Pertussis continues to be the most common vaccine preventable illness in Australia, with periodic epidemics occurring at intervals of 3 to 5 years on a background of endemic circulation (Figure 42). In 2003 there were 5,106 cases notified (25.7 cases per 100,000 population).

Figure 42. Notifications of pertussis, Australia, 1996 to 2003, by month of onset

The highest notification rates were among children aged <1 year (88.2 cases per 100,000 population) and those aged 10–14 years (74.4 cases per 100,000 population) (Figure 43). The overall male to female ratio was 0.8:1.

Figure 43. Notification rate for pertussis, Australia, 2003, by age group and sex

Torvaldsen and McIntyre examined the notification rates of pertussis in children aged 5–9 years in Australia after the introduction of the fifth dose of pertussis vaccine in 1994.¹² As evident in Figure 43, the rates of pertussis in this age group have fallen dramatically, from 193 cases per 100,000 population in 1997 to 17.7 cases per 100,000 population in 2003. Pertussis rates were highest in the 10–14 year age group between 1999 and 2001, but in the last two years, rates in this age group have fallen below those in the 0year age group. A study of 140 infants hospitalised for pertussis in 2001 showed that 45 per cent were less than eight weeks of age (before the first scheduled dose of DTPa vaccine). Sixty-eight per cent of infants had contact with an adult, usually a parent with a cough. This study highlights the need for alternate strategies, which could include accelerated pertussis vaccine schedules for infants, the subject of ongoing research, and/or adult-formulated booster pertussis vaccines for adolescents and recent parents, as recently recommended in Australia.^13,14

Notification rates of pertussis varied considerably by geographic location. The highest rates were in the Australian Capital Territory (110 cases per 100,000 population) and the lowest in the Northern Territory (2.5 cases per 100,000 population). Tasmania and New South Wales also recorded rates of pertussis above the national average in 2003 (Figure 44).

There was an outbreak of pertussis in the Australian Capital Territory in 2003, where a total of 339 cases were reported to the Australian Capital Territory health department from May to December 2003. Each case reported to the Australian Capital Territory health department was followed up individually and advice and education were given. Prophylactic antibiotics were recommended for household contacts if the index case had been coughing for less than three weeks. If a child was assessed to be at risk of contracting pertussis it was recommended that they be seen by a medical practitioner. Workplaces and schools where cases had occurred were notified and sent pertussis fact sheets. Information was also sent to general practitioners, schools, preschools, childcare centres and emergency services.

Figure 44. Notification rates of pertussis, the Australian Capital Territory, New South Wales, Tasmania and Australia, 1999 to 2003 by month of notification

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Pneumococcal disease (invasive)

There were 2,174 notifications of invasive pneumococcal disease (IPD) in Australia in 2003 giving a rate of 10.9 cases per 100,000 population. While the largest numbers of cases were reported from New South Wales, Queensland and Victoria (Table 1), the highest rates were in the Northern Territory (36.3 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 is largely a disease of the very young and very old. The highest rates of disease in 2003, were among children aged less than 5 years (54 cases per 100,000 population, with peak rates in those aged less than 2 years) and adults aged more than 85 years (53.9 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, 2003, by age and sex

Additional data were collected on cases of invasive pneumococcal disease in all Australian jurisdictions during 2003. Analyses of these data have recently been published.¹⁵

Poliomyelitis

No cases of poliomyelitis were reported in Australia in 2003.

There were 44 notifications of acute flaccid paralysis (AFP) reported in 2003. Of these, 33 occurred in children aged less than 15 years. This number represents 83 per cent of the indicator target for AFP set by WHO as consistent with adequate AFP reporting. No poliovirus was isolated from any AFP case.¹⁶

Rubella

In 2003, there were 55 notifications for rubella, a notification rate of 0.3 cases per 100,000 population. This is the lowest rate on record and markedly lower than in 2002 (253 notifications, 1.3 per 100,000 population, Table 4). Unlike trends in the rest of Australia, rates in Queensland increased in 2001 to 2002. However, in 2003 the rate for Queensland fell to be close to rates for other jurisdictions (Figure 46).

Figure 46. Notifications of rubella, Queensland and Australia, 1999 to 2003

As in the past three years, notification rates were highest in males aged 20–24 years (1.9 cases per 100,000 population; Figure 47). Rates for this age group increased between 1999 and 2002, but were much lower in 2003. The male to female ratio of notified cases has been driven by these trends; increasing between 1999 (M:F ratio: 1.4:1) and 2002 (M:F ratio: 3.0:1) but declining in 2003 (M:F ratio: 1.6:1).

Figure 47. Notification rate for rubella, Australia, 2003, by age group and sex

In 2003, Queensland accounted for 43 per cent of all notified cases of rubella (notification rate 0.7 cases per 100,000 population). Ongoing transmission of rubella in Queensland, especially the high rates in 2002, resulted in two locally acquired cases of congenital rubella syndrome in 2003. 17,18 Altogether there were 16 cases of rubella notified from women of child bearing age (15–49 years) in 2003. This number was 40 fewer than in 2002 and the lowest number on record.

Tetanus

Since 1999, two to eight cases of tetanus have been notified each year (Table 4). In 2003, there were four reported cases (one female, three male). One case was in the age range 65–69 years and the other three were all aged more than 85 years.

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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 2003 are shown in Table 13, Table 14 and Table 15 respectively.

Table 13. Percentage of Australian children born in 2002 vaccinated according to data available on the Australian Childhood Immunisation Register, estimate at one year of age

	Percentage vaccinated
Vaccine	1 Jan–31 Mar 2002	1 Apr–30 Jun 2002	1 Jul–30 Sep 2002	1 Oct–31 Dec 2002
DTP	92.2	92.9	92.5	92.4
OPV	92.1	92.8	92.3	92.3
Hib	94.9	94.8	94.4	94.5
Hepatitis B	94.6	95.3	94.8	94.7
Fully vaccinated	91.2	91.7	91.0	91.1

DTP Diphtheria-tetanus-pertussis

OPV Oral polio vaccine

Table 14. Percentage of Australian children born in 2001 vaccinated according to data available on the Australian Childhood Immunisation Register, estimate at two years of age

	Percentage vaccinated
Vaccine	1 Jan–31 Mar 2001	1 Apr–30 Jun 2001	1 Jul–30 Sep 2001	1 Oct–31 Dec 2001
DTP	91.3	91.3	95.8	95.6
OPV	95.0	95.1	94.7	94.7
Hib	93.8	94.0	93.2	93.3
MMR	94.1	94.1	93.4	93.4
Hepatitis B	95.7	95.8	95.6	95.5
Fully vaccinated	89.3	89.2	91.6	91.5

DTP Diphtheria-tetanus-pertussis

OPV Oral polio vaccine

Hib Haemophilus influenzae type b

MMR Measles-mumps-rubella

Table 15. Percentage of Australian children born in 1997 vaccinated according to data available on the Australian Childhood Immunisation Register, estimate at six years of age

	Percentage vaccinated
Vaccine	1 Jan–31 Mar 1997	1 Apr–30 Jun 1997	1 Jul–30 Sep 1997	1 Oct–31 Dec 1997
DTP	84.4	85.0	85.4	85.2
OPV	84.6	85.1	85.6	85.3
MMR	83.7	84.4	84.9	84.7
Fully vaccinated	82.3	83.1	83.7	83.5

DTP Diphtheria-tetanus-pertussis

OPV Oral polio vaccine

MMR Measles-mumps-rubella

 

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.