Vaccine Preventable Diseases in Australia, 2005 to 2007

3.6 Measles

Page last updated: 24 December 2010

Measles is an acute and highly communicable disease caused by a morbillivirus. The clinical picture includes a prodromal fever followed by a generalised maculopapular rash that often begins on the face. There are also frequently Koplik spots on the buccal mucosa, conjunctivitis, coryza and cough. Complications include otitis media, pneumonia and encephalitis. Subacute sclerosing panencephalitis (SSPE) occurs very rarely as a late sequel of infection by the wild-type virus but not following vaccination.1 Complications and deaths are rare, but occur more commonly in developing countries, in children aged <5 years and adults, and in persons with malnourishment or immune deficiencies.2

Top of page

Case definitions

Notifications

See Appendix 6.6 for pre-2004 definition

National definition from January 2004:3

Both confirmed and probable cases are notifiable.

  1. Isolation of measles virus (confirmed case); or
  2. Detection of measles virus by nucleic acid testing (confirmed case); or
  3. Detection of measles virus antigen (confirmed case); or
  4. Measles virus-specific immunoglobulin (Ig) G seroconversion or significant increase in IgG antibody level or a 4-fold or greater rise in antibody titre to measles virus, with paired sera tested in parallel and in the absence of receipt of measles-containing vaccine 8 days to 8 weeks prior to testing (confirmed case); or
  5. Detection of measles virus-specific IgM antibody confirmed in an approved reference laboratory, in the absence of receipt of measles-containing vaccine 8 days to 8 weeks prior to testing (confirmed case); or
  6. A clinical illness characterised by a generalised maculopapular rash lasting at least 3 days, with fever of at least 38°C at the time of rash onset and either cough, coryza, conjunctivitis or Koplik spots, together with an epidemiological link to a confirmed case (confirmed case); or
  7. A clinical illness characterised by a generalised maculopapular rash lasting at least 3 days, with fever of at least 38°C at the time of rash onset and either cough, coryza, conjunctivitis or Koplik spots, together with the detection of measles-specific IgM antibody by a laboratory which is not an approved reference laboratory, except if the case has received a measles-containing vaccine 8 days to 8 weeks prior to testing (probable case).

Hospitalisations and deaths

The ICD-10-AM/ICD-10 code B05 (measles) was used to identify hospitalisations and deaths. SSPE, a very rare late sequel of measles infection, was not included in these analyses.

Top of page

Secular trends

In the 2-year review period of 2006 and 2007, there were 137 notified cases of measles, an average annual notification rate of 0.33 per 100,000 population (Table 3.6.1). Of these 137 cases, 128 (93%) were confirmed cases, and only 9 (7%) probable cases (all notified in 2006). The number of measles notifications in 2006 (n=125) was high compared to both the previous year (n=10) and to 2007 (n=12). The large increase in 2006 was driven by a multi-jurisdictional measles outbreak in March to May of that year, which is described further below (see Geographical distribution). The median number of notifications per month in 2006 was 2 (range 0–59) and in 2007 was 1 (range 0–3).

In the period from July 2005 to June 2007, there were 56 hospitalisations with the ICD-10-AM code B05 (measles). This equates to an average annual hospitalisation rate of 0.14 per 100,000 population. Since a decline in the mid-1990s, annual hospitalisation rates have been at a fluctuating low level, and, in 2006/2007, was the lowest on record at 17 separations, a rate of 0.08 per 100,000. In 2006/2007, the 5-year age groups with the highest rates of hospitalisations were the 0–4 and 25–29 years age groups (0.38 and 0.43 per 100,000, respectively). As with notifications, the peak in the number of hospitalisations per month occurred during the autumn months of March (n=8), April (n=16) and May (n=6) 2006 (Figure 3.6.1). The median number of hospitalisations per month was 1 (range 0–16) in the period July 2005 to June 2007.

Figure 3.6.1: Measles notifications and hospitalisations, Australia, 1993 to 2007,* by month of diagnosis or admission

Figure 3.6.1:  Measles notifications and hospitalisations, Australia, 1993 to 2007, by month of diagnosis or admission

* Notifications where the date of diagnosis was between January 1993 and December 2007; hospitalisations where the date of admission was between July 1993 and June 2007.

Table 3.6.1: Measles notifications, hospitalisations and deaths, Australia, 2005 to 2007,* by age group

Age group
(years)
Notifications
2 years
(2006–2007)
Hospitalisations
2 years
(July 2005–June 2007)
LOS per admission
(days)
Deaths
2 years
(2005–2006)
n Rate n (§) Rate (§) Median (§) n Rate
0–4
33
1.25
16
(14)
0.62
(0.54)
1.0
(1.0)
0
5–14
40
0.73
5
(5)
0.09
(0.09)
2.0
(2.0)
0
15–24
23
0.40
10
(10)
0.18
(0.18)
2.0
(2.0)
0
25–59
40
0.20
25
(23)
0.12
(0.11)
2.0
(2.0)
0
60+
1
0.01
0
(0)
(–)
0
All ages
137
0.33
56
(52)
0.14
(0.13)
2.0
(2.0)
0

* Notifications where the date of diagnosis was between January 2006 and December 2007; hospitalisations where the date of separation was between July 2005 and June 2007; deaths where the death was recorded between January 2005 and December 2006.

† LOS = length of stay in hospital.

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

§ Principal diagnosis (hospitalisations).

Top of page

Severe morbidity and mortality

In the 2-year period from July 2005 to June 2007, hospital separations for measles accounted for 138 hospital bed days. The median length of stay was 2 days, with little variation across the age groups (Table 3.6.1). Of the 56 hospitalisations, 52 (93%) had measles recorded as the principal diagnosis. Complications arising from measles infection were recorded for 9 (16%) separations, of which 5 were coded as having measles complicated by pneumonia and 4 as having complications other than pneumonia, otitis media, encephalitis or meningitis (Table 3.6.2). All hospitalisations coded with measles complicated by pneumonia were aged either <5 years or 25–59 years.

There were no deaths from measles recorded in the AIHW National Mortality Database in 2005 or 2006 (Table 3.6.1).

Table 3.6.2: Selected indicators of severe morbidity* for hospitalised cases of measles, Australia, 2005 to 2007,* by age group

Age group
(years)
Measles complicated by pneumonia Measles with complications other than pneumonia, otitis media, encephalitis or meningitis Measles without complications
n % Total n % Total n % Total
0–4
2
12.5
2
12.5
12
75.0
5–14
0
1
20.0
4
80.0
15–24
0
1
10.0
9
90.0
25–59
3
12.0
0
22
88.0
60+
0
0
0
All ages
5
8.9
4
7.1
47
83.9

* Based on National Hospital Morbidity data where the date of hospital separation was between July 2005 and June 2007.

† % of total in the age group.

Top of page

Age and sex distribution

In 2006–2007, the highest notification rate for measles was seen in the <5 years age group, and the notification rates were progressively lower with increasing age (Table 3.6.1, Figure 3.6.2).

Notification rates for all age groups returned to very low levels in 2007 after the resurgence in 2006. Most notably, notifications in children aged <5 years decreased from 2.22 per 100,000 population in 2006 to 0.30 per 100,000 in 2007 (Figure 3.6.2). Additionally, in 2007, for the first time since the Measles Control Campaign in 1998, there were no cases recorded in adults aged ≥35 years. In both 2006 and 2007, the notification rate for the 0–4 years age group returned to being the highest of all groups, after the previous 3 years in which the 20–34 years age group had the highest rate (Figure 3.6.2).

Figure 3.6.2: Measles notification rates, Australia, 1999 to 2007,* by age group and year of diagnosis

Figure 3.6.2:  Measles notification rates, Australia, 1999 to 2007, by age group and year of diagnosis

* Notifications where the date of diagnosis was between January 1999 and December 2007.

Top of page

From July 2006 to June 2007, hospitalisation rates were the lowest on record for the 0–4 years (0.38 per 100,000) and ≥35 years (0.00 per 100,000) age groups (Figure 3.6.3). No hospitalisations were recorded for persons aged ≥35 years. Hospitalisation rates for both the 5–9 years and 10–19 years age groups also decreased over the review period July 2005 to June 2007, returning to levels comparable to those observed in the previous 3 years. Hospitalisation rates for the 0–4 years age group have consistently been the highest of all age groups since reporting began, and, since 2000/2001, persons 20–34 years of age have had the second highest hospitalisation rate (Figure 3.6.3).

Figure 3.6.3: Measles hospitalisation rates, Australia, 1998/1999 to 2006/2007,* by age group and year of separation

Figure 3.6.3:  Measles hospitalisation rates, Australia, 1998/1999 to 2006/2007, by age group and year of separation

* Hospitalisations where the date of separation was between July 1998 and June 2007.

Over the 2-year period 2006–2007, there were slightly more notifications for females than males (male:female ratio 1:1.1). However, more males were hospitalised than females (male:female ratio 1.3:1).

Top of page

Geographical distribution

There were 125 measles notifications in 2006, of which 82 (66%) occurred as a result of a multi-jurisdictional outbreak associated with an Indian spiritual group that toured Australia from March to May 2006. Only 7% of the cases in that outbreak were fully immunised against measles, while two-thirds were unimmunised.4 Another separate outbreak consisting of 3 primary cases and 8 secondary cases was linked to an Emergency Department in New South Wales on 1 March 2006. The index case was believed to be a sick traveller; however, this could not be confirmed.5 One case was imported from Europe in March 2006 but no related secondary transmission was detected, despite enhanced surveillance measures implemented at the time for the 18th Commonwealth Games in Melbourne.6 Several other Victorian cases had a recent history of overseas travel; however, some additional cases were identified where travel outside the state during the incubation period had not occurred.7–10 In 2006–2007, 17 cases were recorded in NNDSS as acquired overseas. For a further 18 cases, this information was unknown or missing. The remaining 102 cases were recorded as locally acquired, but it is unknown how many of these were linked to an imported case, as this information is not routinely collected at national level.

Measles cases were notified from all jurisdictions, except the Northern Territory, during the period 2006–2007. The rate of notification over the reporting period was highest in Tasmania with 1.12 per 100,000 population (n=11), followed by Western Australia with 0.74 per 100,000 (n=31). In both states, these rates were more than twice the national rate of 0.33 per 100,000. The increased notification rates in most jurisdictions during the review period were largely due to the multi-jurisdictional outbreak described above.

There was little variation during 2006–2007 between jurisdictional rates of hospitalisation for those regions with hospitalised cases (Appendix 6.3).

Top of page

Measles typing and vaccination status

Measles virus genotype was recorded in NNDSS for 20 cases (15%) notified during the reporting period 2006–2007. The majority of these were D8, the genotype confirmed as the cause of the 2006 multi-state outbreak imported by the Indian spiritual group.4 Other genotypes noted in NNDSS included D4 and D5, and the case in Victoria in March 2006 was identified as genotype B3, most likely contracted during travel in Germany.6

Vaccination status is expected to be completed in NNDSS for all notifications of measles in people born after 31 December 1969. Overall, 89% (116/130) of cases who were born after this date and notified in the review period had this field completed. Of the 123 cases aged ≥1 year among these 130 notified cases, 14 were reported as fully vaccinated for age, of which 5 were aged 1–3 years and thus had received only 1 dose of measles-containing vaccine; a further 9 were recorded as partially vaccinated for age, and 86 as unvaccinated. The remaining 7 of the 130 cases were aged <1 year and were thus most likely too young to have received any dose of measles-containing vaccine. Vaccination status was validated by written records in 43% (6/14) of the cases reported to be fully vaccinated, 20% (2/10) of partially vaccinated cases, and 28% (26/92) of cases whose vaccination status was recorded as unvaccinated or ‘not applicable’.

Top of page

Comment

In the 2-year review period 2006–2007, with the exception of the outbreak between March and May 2006, measles notifications and hospitalisations remained at very low rates. Measles accounted for only 12 notifications in 2007 and 17 hospitalisations between July 2006 and June 2007. The overall long-term downward trend is similar to that seen in other countries with high vaccination coverage. Endemic measles has been eradicated in the USA since 200011,12 and transmission has been interrupted in most other countries across the Americas.13 Indigenous measles was declared to be eliminated in England and Wales following an intensive school-based vaccination program in 1994.14 However, since that time, vaccination coverage in the UK decreased significantly, mostly associated with the controversy regarding the safety of the measles-mumps-rubella (MMR) vaccine. As a result the proportion of susceptible children aged 2–4 years has been estimated to be 27% in 2004/2005,15 a level sufficient to support the continuous endemic spread of measles.16 Despite all the gains made in measles control in recent decades, outbreaks continue to occur in unvaccinated groups throughout Europe17 and in the USA.18

Notwithstanding the progress made in countries with high vaccination coverage, travellers remain at increased risk of measles exposure in many countries where high vaccination coverage has not been achieved and endemic measles transmission still occurs. In 2007, global measles-containing vaccine coverage was estimated to be 82%. However, this varied significantly geographically, with coverage in the Western Pacific region at over 90%.19 The global measles disease burden continues to decrease but there were still an estimated 279,000 cases in 2007 and 242,000 deaths in 2006.19 Despite the progress made in improving measles surveillance activities by many countries, these figures are still likely to be an underestimate.20

Where endemic measles has been eliminated, enhanced surveillance including laboratory confirmation is required and recommended by the World Health Organization (WHO).21 Therefore, in Australia, laboratory evidence or linkage to a chain of transmission that includes a laboratory-confirmed case is now required in the case definition for notification and this is the first review period for which this has been consistent at a national level for the whole period.

The WHO Regional Committee for the Western Pacific set a target date of 2012 for elimination of endemic measles transmission in the region.22 Mathematical modelling of vaccine coverage and data generated from the two previous serosurveys in Australia have demonstrated that the effective reproductive number R (the average number of secondary cases produced by a typical primary case in a given population) is less than 1 and this is predicted to remain the case until at least 2012.23,24 Consistently high 2-dose vaccine coverage, serological evidence of very high population immunity and a high proportion of cases imported or linked to an imported case, as well as sustained maintenance of an R of less than 1, indicate that endemic transmission has already been eliminated in Australia since 2005.22 Continued monitoring is still required, however, as Australia has not yet achieved a residual population susceptibility of 5% following completion of the 2-dose schedule, which is required for long-term sustained measles elimination.23 Furthermore, vaccine coverage varies geographically and between age groups. Thus certain regions or birth cohorts with low proportions of immune individuals may allow some sustained transmission of measles if it is imported into that cohort, although secondary transmission in the vaccinated population would be extremely limited.24

Top of page

The current 2-dose measles vaccine schedule began in 1998 following the mass vaccination of primary school aged children as part of the Measles Control Campaign.25 Since then, consistently high vaccination coverage prior to school entry has been maintained and, as discussed above, this has contributed to the elimination of endemic measles transmission in Australia.22,26 However, the high level of vaccine coverage in children and reduced exposure to naturally circulating measles virus have left a residual cohort of susceptible young adults born in the late 1970s and early 1980s, when measles vaccine was first introduced but coverage was low. To improve immunity in this birth cohort, the young adult MMR vaccination campaign was undertaken during 2001.25 However, a serosurvey conducted in 2002 indicated that immunity in the young adult cohort did not significantly improve.23 It also indicated Australia had reached WHO age-specific susceptibility targets in children <10 years of age but not in older age groups, with a relatively high proportion (9%) of targeted young adults remaining susceptible.27 This was reflected in the notification data from 2003–2005 when the notification rate for 20–34 year olds was the highest of all age groups. However, in the current review period, the 0–4 years age group has again returned to having the highest notification rate.

Despite the elimination of endemic transmission, Australia remains at risk of measles importation from countries where measles is still endemic.26 The source case of most measles outbreaks had a recent overseas travel history and molecular genotyping of measles isolates provided confirmation of imported strains,28 but some outbreaks have not had a source case identified.

In summary, the notification data show a relative decrease in measles cases in young adults and that very low rates of background measles cases have been maintained. However, the potential for relatively large outbreaks, such as the one that occurred in early 2006, still exists and ongoing efforts to increase uptake of the MMR vaccine need to be maintained to decrease residual susceptibility to below 5%. Children aged <5 years have the highest rates of measles infection and hospitalisation of any age group, suggesting that high coverage, including better timeliness and completeness of childhood vaccinations among preschool aged children, should remain an important goal of Australia’s measles control strategy if we are to avoid a return of endemic measles transmission such as that currently occurring in England.15

Top of page

References

1. Measles. In: Heymann DL, ed. Control of Communicable Diseases Manual. 19th edn. Washington, DC: American Public Health Association, 2008.

2. Perry RT, Halsey NA. The clinical significance of measles: a review. J Infect Dis 2004;189(Suppl 1):S4–S16.

3. Communicable Diseases Network Australia. Surveillance case definitions for the Australian National Notifiable Diseases Surveillance System. 2004. Available from: http://www.health.gov.au/internet/main/publishing.nsf/Content/cdna-casedefinitions.htm Accessed on 24 August 2009.

4. Begg K, Roche P, Owen R, Liu C, Kaczmarek M, Hii A, et al. Australia’s notifiable diseases status, 2006: annual report of the National Notifiable Diseases Surveillance System. Commun Dis Intell 2008;32(2):139–207.

5. NSW Department of Health. Communicable diseases report, New South Wales, for March and April 2006. N S W Public Health Bull 2006;17(5–6):88–94.

6. Riddell MA, Lynch P, Jin L, Chibo D. Measles case imported from Europe to Victoria, Australia, March 2006. Euro Surveill 2006;11(20):p11=2959. Available from: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=2959 Accessed on 5 March 2009.

7. Fielding J. Surveillance report. Vaccine-preventable diseases: measles. Victorian Infectious Diseases Bulletin 2006;9(2):44.

8. Fielding J. Surveillance report. Vaccine-preventable diseases: measles. Victorian Infectious Diseases Bulletin 2006;9(3):72.

9. Fielding J. Surveillance report. Vaccine preventable diseases: measles. Victorian Infectious Diseases Bulletin 2007;10(1):12.

10. Fielding J. Surveillance report. Vaccine preventable diseases: measles. Victorian Infectious Diseases Bulletin 2007;10(2):44.

11. Katz SL, Hinman AR. Summary and conclusions: measles elimination meeting, 16–17 March 2000. J Infect Dis 2004;189(Suppl 1):S43–S47.

12. Orenstein WA, Papania MJ, Wharton ME. Measles elimination in the United States. J Infect Dis 2004;189(Suppl 1):S1–S3.

13. de Quadros CA, Andrus JK, Danovaro-Holliday MC, Castillo-Solórzano C. Feasibility of global measles eradication after interruption of transmission in the Americas. Expert Rev Vaccines 2008;7(3):355–362.

14. Ramsay ME, Jin L, White J, Litton P, Cohen B, Brown D. The elimination of indigenous measles transmission in England and Wales. J Infect Dis 2003;187(Suppl 1):S198–S207.

15. Choi YH, Gay N, Fraser G, Ramsay M. The potential for measles transmission in England. BMC Public Health 2008;8:338.

16. Editorial team. Measles once again endemic in the United Kingdom. Euro Surveill 2008;13(27):p11=18919. Available from: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=18919 Accessed on 5 March 2009.

17. Muscat M, Bang H, Glismann S. Measles is still a cause for concern in Europe. Euro Surveill 2008;13(16):p11=18837. Available from: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=18837 Accessed on 5 March 2009.

18. Centers for Disease Control and Prevention. Update: measles—United States, January–July 2008. MMWR Morb Mortal Wkly Rep 2008;57(33):893–896.

19. World Health Organization. Immunization surveillance, assessment and monitoring. Measles. Geneva, World Health Organization, 2008. Available from: http://www.who.int/immunization_monitoring/diseases/measles/en/ Accessed on 20 October 2008.

Top of page

20. Centers for Disease Control and Prevention. Progress in global measles control and mortality reduction, 2000–2007. MMWR Morb Mortal Wkly Rep 2008;57(48):1303–1306.

21. World Health Organization, United Nations Children’s Fund (UNICEF). WHO/UNICEF joint statement. Global plan for reducing measles mortality, 2006–2010. Geneva, World Health Organization, 2006. Available from: http://www.who.int/vaccines-documents/DocsPDF06/WHO_IVB_05_11.pdf Accessed on 15 October 2008.

22. Heywood AE, Gidding HF, Riddell MA, McIntyre PB, MacIntyre CR, Kelly HA. Elimination of endemic measles transmission in Australia. Bull World Health Organ 2009;87(1):64–71.

23. Gidding HF, Wood J, MacIntyre CR, Kelly H, Lambert SB, Gilbert GL, et al. Sustained measles elimination in Australia and priorities for long term maintenance. Vaccine 2007;25(18):3574–3580.

24. MacIntyre CR, Gay NJ, Gidding HF, Hull BP, Gilbert GL, McIntyre PB. A mathematical model to measure the impact of the Measles Control Campaign on the potential for measles transmission in Australia. Int J Infect Dis 2002;6(4):277–282.

25. Turnbull FM, Burgess MA, McIntyre PB, Lambert SB, Gilbert GL, Gidding HF, et al. The Australian Measles Control Campaign, 1998. Bull World Health Organ 2001;79(9):882–888.

26. Gidding HF. The impact of Australia’s measles control programme over the past decade. Epidemiol Infect 2005;133(1):99–105.

27. Andrews N, Tischer A, Siedler A, Pebody RG, Barbara C, Cotter S, et al. Towards elimination: measles susceptibility in Australia and 17 European countries. Bull World Health Organ 2008;86(3):197–204.

28. Chibo D, Riddell M, Catton M, Lyon M, Lum G, Birch C. Studies of measles viruses circulating in Australia between 1999 and 2001 reveals a new genotype. Virus Res 2003;91(2):213–221.

Document download

This publication is available as a downloadable document.

Vaccine Preventable Diseases in Australia, 2005 to 2007(PDF 1217 KB)