This article {extract} was published in Communicable Diseases Intelligence Vol 30 No 1 March 2006 and may be downloaded as a full version PDF from the Table of contents page.
Results, continued
Vaccine preventable diseases
Introduction
This section summarises the national notification data for influenza and diseases targeted by the Australian Standard Vaccination Schedule (ASVS) except varicella in 2004. 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' respectively. Other vaccine preventable diseases presented in this report include hepatitis A and Q fever.
The main change to the ASVS relevant to this reporting period was the removal of the fourth dose of the DTPa vaccine, due at 18 months of age, which occurred in September 2003. In 2004, Western Australia and New South Wales ran school-based programs to deliver dTpA vaccine to adolescents.
There were 13,206 notifications of vaccine preventable diseases (VPDs) with onset dates in 2004; 11.9 per cent of the total notifications to NNDSS. Pertussis was the most commonly notified VPD (8,557 or 65% of all VPD notifications). Numbers of notifications and notification rates for VPDs in Australia are shown in Tables 2 and 3.
Diphtheria
Case definition – Diphtheria Both confirmed cases and probable cases are reported. Confirmed case: Requires isolations of toxigenic Corynebacterium diphtheriae or toxigenic C. ulcerans. Probable case: Requires isolation of Corynebacterium diphtheriae or C. ulcerans (toxin production unknown) and pharyngitis/laryngitis or toxic symptoms OR clinical symptoms and epidemiological links with laboratory confirmed case. |
There were no cases of diphtheria reported in 2004. The last case of diphtheria reported in Australia was a case of cutaneous diphtheria in 2001.
Haemophilus influenzae type b
Case definition – Haemophilus influenzae type b Only confirmed cases are reported. Confirmed case: Requires isolation of Haemophilus influenzae type b (Hib) from a sterile site OR detection of Hib antigen in cerebrospinal fluid consistent with meningitis. |
Notifications of Haemophilus influenzae type b (Hib) have fallen more than 30–fold since 1991 due to the impact of Hib conjugate vaccines. 11 There were 15 notifications of Hib disease in 2004, a rate of 0.1 cases per 100,000 population. This is eight (35%) fewer cases than reported in 2003, and is the lowest number of notifications recorded since national surveillance began in 1991. Five cases (33% of total cases) were in children aged less than 5 years and two were infants aged less than 1 year (Figure 38). There were eight cases in males and seven in females, (male: female ratio 1.1:1).
Figure 38. Notifications of Haemophilus influenzae type b infection, Australia, 2004 by age group and sex
TheNorthern Territory had the highest notification rate (1.5 cases per 100,000 population, 3 cases) although most cases were from New South Wales (n=5).
Of the 14 cases with a known Indigenous status, two were Indigenous and 12 were non-Indigenous. Indigenous children now make up a greater proportion of cases than in the pre-immunisation era.11 In a review of vaccine preventable disease in Indigenous people, 2000 to 2002, Menzies, et al observed a notification rate of Hib in Indigenous which was 9.7 times that in non-Indigenous people.12 In 2004, the Hib notification rate was 0.4 per 100,000 in Indigenous people and 0.06 per 100,000 in non-Indigenous people – a ratio of 6.7:1.
Cases under the age of 15 years were eligible for vaccination. The vaccination status of 9 of these 10 cases was known—two were unvaccinated, one partially vaccinated and six met the definition for vaccine failure, having received at least 2 doses under the age of 12 months. Of the vaccine failures, 3 (50%) were aged under 5 years.
A recent evaluation of the impact of Hib vaccination on Hib meningitis in Far North Queensland shows a dramatic decline in the incidence of this disease. In the four years prior to the addition of Hib vaccines to the ASVS, there were 28 cases of Hib meningitis in Far North Queensland and the rate of disease was 3.5 times greater in Indigenous children compared with non-Indigenous children. Since 1993, there has only been a single case of Hib meningitis, which was in a non-Indigenous child. The authors of this study estimated that in their region, Hib vaccination had prevented 70 cases of disease, five deaths and 12 cases with neurological sequelae.13
Influenza
Case definition – Influenza Only confirmed cases are notified. Confirmed case: Requires isolation of influenza virus by culture OR detection of influenza virus by nucleic acid testing OR detection of influenza virus antigen from an appropriate respiratory tract specimen OR a significant increase in antibody levels, or IgG seroconversion or fourfold or greater rise in antibody titre or a single high titre antibody. |
There were 2,073 reports of laboratory-confirmed influenza in 2004, a rate of 10.3 cases per 100,000 population. Notifications of influenza showed a peak in September 2004 (Figure 39).
Figure 39. Notifications of laboratory-confirmed influenza, Australia, 2004, by month of onset
Children aged less than 5 years made up 21 per cent of all notifications and had a notification rate of 34.8 cases per 100,000 population (Figure 40). Children aged less than 1 year had the highest rates (63.1 cases per 100,000 population). The overall male to female ratio was 1:1.
There were 72 notifications of influenza in Indigenous people in 2004. This gives a notification rate for influenza of 14.8 per 100,000 compared with 10 per 100,000 in non-Indigenous people—a rate ratio of 1.5:1. A higher rate of hospitalisation for influenza in Indigenous people was noted between 2000 and 2002.12
Figure 40. Notification rate of laboratory-confirmed influenza, Australia, 2004, by age group and sex
In 2004, 1,896 (91%) of notifications had serotype data. Of these 79 per cent (1,493) were influenza A and 21 per cent (403) were influenza B.
Of 454 isolates analysed at the WHO Collaborating Centre for Reference and Research on Influenza in 2004, 342 were A(H3N2), 3 were A(H1N1) strains and 108 were influenza B. The majority of A(H3N2) viruses were A/Fujian/411/2002(H3N2)-like with significant antigenic drift and were similar to the recent A/Wellington/1/2004 isolate.
In 2004, 79 per cent of those aged 65 years and over in Australia received influenza vaccination.14
There were a number of outbreaks of influenza in 2004. Two outbreaks occurred in army barracks, one in Victoria and another in Queensland. There were 13 outbreaks of influenza-like illness in 12 aged care facilities in New South Wales, marked by high attack rates (76% in residents and 42% in staff) and a case fatality rate of 14 per cent.
Measles
Case definition – Measles Both confirmed cases and probable cases are notified. Confirmed case: Requires isolation of measles virus or detection of measles virus by nucleic acid testing OR detection of measles virus antigen OR IgG seroconversion or significant increase in antibody level or fourfold or greater rise in titre or detection of measles specific IgM antibody in a reference laboratory (except when vaccinated 8 days to 8 weeks prior to testing) OR clinical illness characterised by a maculopapular rash and fever and cough, coryza, conjunctivitis or koplik spots and epidemiological link to a laboratory confirmed case. Probable case: Requires detection of measles IgM antibody in other than an approved reference laboratory and clinical illness. |
There were 45 measles cases in 2004, including 43 confirmed and 2 probable cases; a national rate of 0.2 cases per 100,000 population. This was a 54 per cent decrease compared with 2003 when 98 cases were notified, and is the second lowest annual rate for Australia since national surveillance began in 1991 (Figure 41). The highest rate was in the Northern Territory with 1.5 cases per 100,000 population (3 cases), while the largest number of cases were reported from Victoria (15 cases, 0.3 cases per 100,000 population). In 2004 there were no cases reported from the Australian Capital Territory, Queensland or Tasmania (Tables 2 and 3).
Figure 41. Notifications of measles, Australia, 1997 to 2004, by month of onset
Notification rates were highest in the 25–29 year age group (1.2 cases per 100,000 population), followed by the 0–4 and 30–34 year age groups (0.5 cases per 100,000 population, Figure 42). There were only six cases in the under 5 year age group and three were aged less than 1 year (0.8 cases per 100,000 population).
Figure 42. Trends in notification rates of measles, Australia, 1999 to 2004, by age group
Figure 42 shows trends in measles notification rates by age group. In 2004 the largest proportion of measles cases occurred in adults, which reflects the success of measles vaccination programs in children and adolescents. A recent review suggests that indigenous transmission of measles has been interrupted and that Australia is making good progress toward measles elimination.15
Of the 45 measles cases reported in 2004, 21 (46%) occurred in six outbreaks in three states (Table 17). The index case in four of the six outbreaks acquired their infection outside Australia.
Table 17. Outbreaks and clusters of measles, Australia,* 2004
State or territory |
Month of onset | Number of linked cases (including index case) |
Place of acquisition of infection in index case |
|---|---|---|---|
| NSW | Mar |
2 |
Overseas |
| NSW | Mar |
4 |
Overseas |
| Victoria | Apr |
2 |
Overseas |
| Victoria | July |
4 |
Victoria |
| Victoria | Nov |
3 |
Overseas |
| WA | Nov |
6 |
Not identified |
* There were no cases of measles reported in 2004 in the Australian Capital Territory, Queensland or Tasmania.
The outbreak in Western Australia is significant because all six cases were in Indigenous people and there was no link to a confirmed imported index case. These were the only measles notification in Indigenous people in 2004, giving a rate of 1.2 per 100,000 population compared with 0.2 per 100,000 in non-Indigenous people (a rate ratio of 6:1).
The vaccination status was recorded for 25 of the 42 cases born after the introduction of measles vaccination in 1970: 19 were unvaccinated, four were partially vaccinated and two were fully vaccinated for age. Both 'fully vaccinated for age' cases had only received a single dose of measles-mumps-rubella (MMR) vaccine: one was a 1-year-old child who was fully vaccinated for age and the other was a 16-year-old who should be regarded as partially vaccinated.
Mumps
Case definition – Mumps Only confirmed cases are notified. Confirmed case: Requires isolation of mumps virus or detection of mumps virus by nucleic acid testing or IgG seroconversion or significant increase in antibodies or a significant increase in antibody level, or a fourfold or greater rise in titre to mumps virus (except where there has been recent mumps vaccination) OR detection of mumps specific IgM antibody (in the absence of recent mumps vaccination) AND a clinically compatible illness characterised by swelling of the parotid or other salivary glands lasting two days or more without other apparent cause OR a clinically compatible illness AND an epidemiological link to a laboratory confirmed case. |
In 2004, there were 102 notifications of mumps, a rate of 0.5 cases per 100,000 population. This was a 24 per cent increase on the 82 cases reported in 2003. Unlike 2003 when there was a preponderance of cases in males (male:female ratio 1.5:1), the male:female ratio in 2004 was 1:1.
The highest rates were in the 25–29 year age group (1.3 cases per 100,000 population). The rate for the 0–4 year age group (0.6 cases per 100,000 population) was similar to that seen in 2003.
Trends in age group notification rates for mumps (Figure 43) show an increase in the rates in the 25–34 year age group since 2003. Increases in mumps in England and Wales, predominately among older teenagers and young adults who had not received two doses of MMR vaccine, have also been observed.16
Figure 43. Trends in notification rates for mumps, Australia, 2004, by age group
Pertussis
Case definition – Pertussis Both confirmed cases and probable cases are notified. Confirmed case: Requires isolation of Bordetella pertussis or detection of B. pertussis by nucleic acid testing OR seroconversion or significant increase in antibody level or fourfold or greater rise in titre (in the absence of pertussis vaccination) or a single high-titre IgA to whole cells or detection of B. pertussis by immunofluorescence AND clinical evidence (a coughing illness lasting 2 weeks or more or paroxysms of coughing or inspiratory whoop or post-tussive vomiting) OR clinical evidence AND epidemiological link to a confirmed case. Probable case: Requires clinically compatible illness. |
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 44). In 2004, there were 8,557 cases (42.5 cases per 100,000 population) notified to NNDSS. Of these, 7,638 were confirmed and 649 were probable cases, while the status of the remaining 270 cases was unknown.
Figure 44. Notifications of pertussis, Australia, 1996 to 2004, by month of onset
The highest notification rates were among children aged <1 year ( 262 cases, 103.1 cases per 100,000 population) and those in the 10–14 year age group (1,112 cases, 80.2 cases per 100,000 population) (Figure 45). The notification rate in persons aged 60 years and over rose dramatically between 2003 and 2004 (13.8 versus 33.6 cases per 100,000 population). This is in contrast to the relatively steady annual rates previously seen in this age group. In 2004, 74 per cent of pertussis cases were aged 15 years or over. Although severe morbidity and mortality are less likely in these age groups, they are an important pertussis reservoir, facilitating transmission to children too young to be fully vaccinated. The overall male to female ratio was 0.8:1.
Figure 45. Trends in notification rates for pertussis, Australia, 1996 to 2004 by age group
Notification rates of pertussis varied considerably by geographic location (Map 6). At the State/Territory level, rates were highest in Western Australia (105.8 cases per 100,000 population) and lowest in Tasmania (7.7 cases per 100,000 population).
Map 6. Notification rates of pertussis, Australia, 2004, by Statistical Division of residence
There was an outbreak of pertussis in the Western Australia in 2004, where the notification rate was the highest since 1997. A relatively large proportion of notifications were in secondary school students, so a mass vaccination campaign with dTpa was instituted in secondary schools. New South Wales also had a school-based dTpa campaign in 2004. New South Wales and South Australia recorded rates of pertussis for all ages above the national average in 2004 (Figure 46).
Figure 46. Notification rates of pertussis, New South Wales, South Australia, Western Australia and Australia, 1999 to 2004, by month of notification
There were 153 cases who were identified as Indigenous (31.6 cases per 100,000 population) and 8,227 who were identified as non-Indigenous (41.9 cases per 100,000 population). The Indigenous pertussis notification rate ratio for all ages was therefore 0.75, but it is important to note that previous analyses have shown that, in the age groups where the disease is most severe, there were higher rates in Indigenous compared to non-Indigenous populations. For example, in 2000–2002 the notification rate ratio for children aged 0–4 years was 1.7, and 2.6 for those aged less than one year.12
A review of cough symptoms in children in Sydney has provided evidence of cases of pertussis which are not notified. Clinically diagnosed pertussis was estimated to be between 5 and 20 times the notification rates.17
Invasive pneumococcal disease
Case definition – Invasive pneumococcal disease Only confirmed cases are notified. Confirmed case: Requires isolation of Streptococcus pneumoniae from a normally sterile site by culture or detection by nucleic acid testing. |
There were 2,375 notifications of invasive pneumococcal disease (IPD) in Australia in 2004 giving a rate of 11.8 cases per 100,000 population. While the largest number of cases were reported from New South Wales, Queensland and Victoria (Table 1), the highest rate was in the Northern Territory (47 cases per 100,000 population). The geographical distribution of IPD varied within states and territories, with the highest rates in Central and northern Australia.
In 2004, IPD remained largely a disease of the very young and very old. The highest rates of disease were among children aged less than 5 years (54.3 cases per 100,000 population, with peak rates in 1-year-olds, 114 cases per 100,000 population) and adults aged more than 85 years (46.3 cases per 100,000 population) (Figure 47). There were more cases among males, with a male to female ratio of 1.4:1.
Figure 47. Notification rate for invasive pneumococcal disease, Australia, 2004, by age group and sex
There were 174 cases of IPD in Indigenous people (35.9 cases per 100,000 population) and 2,201 in non-Indigenous people (11.2 cases per 100,000 population), an Indigenous:non-Indigenous ratio of 3.2:1.
Additional data were collected on cases of invasive pneumococcal disease in all Australian jurisdictions during 2004. Analyses of these data have can be found in the IPD annual report in this issue.18
Poliomyelitis
Case definition – Poliomyelitis Both confirmed cases and probable cases are notified. Confirmed case: Requires isolation of wild-type poliovirus or detection of wild-type poliovirus by nucleic acid testing (confirmed in reference laboratory) and acute flaccid paralysis. Probable case: Requires acute flaccid paralysis not due to other causes as determined by the Polio Expert Committee. |
No cases of poliomyelitis were reported in Australia in 2004.
There were 62 notifications of acute flaccid paralysis (AFP) reported in 2004. Of these 49 occurred in children aged less than 15 years. This represents an AFP notification rate of 1.2 cases per 100,000 children aged less than 15 years and meets the WHO indicator target for adequate AFP reporting. One infant AFP case had Sabin-like polioviruses 1 and 2 isolated from stool. The Polio Expert Committee classified this case as infant botulism based on the detection of Clostridium botulinum serotype B toxin and isolation of C. botulinum serotype B organism from a faecal sample.19
Rubella
Case definition – Rubella Both confirmed cases and probable cases are notified. Confirmed case: Requires isolation of rubella virus OR detection of rubella virus by nucleic acid testing OR IgG seroconversion or significant increase in antibody level or fourfold or greater rise in titre to rubella virus in the absence of recent rubella vaccination, OR detection of rubella specific IgM in the absence of recent rubella vaccination and confirmed in a reference laboratory. Probable case: Requires clinical evidence AND laboratory suggestive evidence OR epidemiological evidence. Laboratory suggestive evidence: In a pregnant patient, detection of rubella-specific IgM that has not been confirmed in a reference laboratory, in the absence of recent rubella vaccination. Clinical evidence: A generalised maculopapular rash AND fever AND arthralgia/arthritis OR lymphadenopathy OR conjunctivitis Epidemiological evidence: An epidemiological link is established when there is: 1. Contact between two people involving a plausible mode of transmission at a time when: a) one of them is likely to be infectious (about one week before to at least four days after appearance of rash) AND b) the other has an illness which starts within 14 and 23 days after this contact AND 2. At least one case in the chain of epidemiologically linked cases (which may involve many cases) is laboratory confirmed. |
In 2004, there were 33 notifications for rubella: 32 confirmed and 1 probable case; a notification rate of 0.2 cases per 100,000 population. This is the lowest rate on record and a 40 per cent reduction on 2003 (55 notifications, 0.3 cases per 100,000 population). In 2004, New South Wales accounted for 52 per cent of all notified cases of rubella (17 cases, notification rate 0.3 cases per 100,000 population) and Queensland 30 per cent (10 cases, 0.3 cases per 100,000 population).
The male to female ratio of notified cases in 2004 was 1:1 in contrast to the male predominance seen in 1999 (male:female ratio 1.4:1), 2002 (male:female ratio 3.0:1) and 2003 (male:female ratio 1.6:1).
Figure 48 shows trends in rubella notification rates in different age groups. The rates in older teenagers and young adults continued to decline in 2004.
Figure 48. Trends in notification rates for rubella,Australia, 2004, by age group and sex
There was a single case of congenital rubella reported from New South Wales in 2004. The child was born to an unvaccinated overseas-born mother. Altogether there were 14 cases of rubella notified from women of child-bearing age (15–49 years) in 2004.
Tetanus
Case definition – Tetanus Only confirmed cases are notified. Confirmed case: Requires isolation of Clostridium tetani from a wound in a compatible clinical setting and prevention of positive tetanospasm in mouse test using a specific tetanus antitoxin OR a clinically compatible illness without other apparent cause. |
In 2004, there were five notifications of tetanus. Four were female and one was male and all were aged over 60 years.
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 2004 are shown in Table 18, Table 19, and Table 20, respectively. Over the four quarters, there were no significant changes in coverage for all three age groups. Coverage of all vaccines used to assess 'fully immunised' status at 24 months of age was higher than for the other two age groups. Coverage for all vaccines at 6 years of age remains significantly lower (8–9 percentage points) than at 12 and 24 months and still is of concern.
Table 18. Percentage of Australian children born in 2003 immunised according to data available on the Australian Childhood Immunisation Register, estimate at one year of age
Vaccine |
1 Jan–31 Mar 200 3 | 1 Apr– 30 Jun 200 3 | 1 Jul–30 Sep 200 3 | 1 Oct–31 Dec 200 3 |
|---|---|---|---|---|
| DTP | 92.3 |
92.7 |
92.6 |
92.2 |
| OPV | 92.2 |
92.6 |
92.5 |
92.0 |
| Hib | 94.5 |
94.8 |
94.8 |
94.4 |
| Hepatitis B | 94.7 |
94.9 |
95.0 |
94.7 |
| Fully immunised | 90.9 |
91.3 |
91.2 |
90.7 |
Table 19. Percentage of Australian children born in 2002 immunised according to data available on the Australian Childhood Immunisation Register, estimate at two years of age
Vaccine |
1 Jan–31 Mar 2002 | 1 Apr–30 Jun 2002 | 1 Jul–30 Sep 2002 | 1 Oct–31 Dec 2002 |
|---|---|---|---|---|
| DTP | 95.5 |
95.3 |
95.0 |
94.9 |
| OPV | 94.9 |
95.2 |
95.0 |
94.8 |
| Hib | 93.4 |
93.8 |
93.4 |
93.2 |
| MMR | 93.5 |
93.9 |
93.6 |
93.4 |
| Hepatitis B | 95.7 |
95.9 |
95.4 |
95.5 |
| Fully immunised | 91.7 |
92.3 |
91.7 |
91.7 |
Table 20. Percentage of Australian children born in 1998 immunised according to data available on the Australian Childhood Immunisation Register, estimate at six years of age
Vaccine |
1 Jan–31 Mar 1998 | 1 Apr–30 Jun 1998 | 1 Jul–30 Sep 1998 | 1 Oct–31 Dec 1998 |
|---|---|---|---|---|
| DTP | 85.2 |
85.4 |
85.2 |
84.7 |
| OPV | 85.2 |
85.3 |
85.2 |
84.8 |
| MMR | 84.8 |
84.8 |
84.8 |
84.6 |
| Fully immunised | 83.5 |
83.6 |
83.6 |
83.3 |
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Communicable Diseases Surveillance
This issue - Vol 30 No 1, March 2006
NNDSS Annual report 2004
Communicable Diseases Intelligence