Impact of the Australian Measles Control Campaign on immunity to measles and rubella.

To evaluate the impact of the 1998 Australian Measles Control Campaign on immunity to measles and rubella, 4400 opportunistically-collected sera, submitted to diagnostic laboratories across Australia from subjects aged 1-49 years, and 3000 from subjects aged 1-18 years, were tested before and after the campaign, respectively. The proportion of individuals aged 1-18 years who were immune to measles rose from 85% before, to 90% after, the campaign (P < 0.001). The greatest increase was in preschool (7%, P < 0.001) and primary school (10%, P < 0.001) children, who were actively targeted by the campaign. Rubella immunity in 1-18 year-olds rose from 83% to 91% (P < 0.0001), again with significant increases in preschool (4%, P = 0.002) and primary school (16%, P < 0.001) children. 94% of individuals aged 19-49 years were immune to rubella. These serosurveys confirm other evidence of the effectiveness of the Australian Measles Control Campaign and demonstrate the value of serosurveillance using opportunistically collected sera.

Hepatitis A epidemiology in Australia: national seroprevalence and notifications.

OBJECTIVES: To determine hepatitis A seroprevalence and notification rates in Australia in order to inform vaccination policy. DESIGN: Seroprevalence was determined by cross-sectional survey of opportunistically collected sera; notifications were extracted from the National Notifiable Diseases Surveillance System. PARTICIPANTS: 3,043 serum samples collected in 1998 were obtained from 46 laboratories around Australia. Sample size in each age group was based on expected seroprevalence, and States and Territories were sampled proportionally to their population size. Males and females were equally represented. Notifications were extracted for cases with onset between 1 January 1991 and 31 December 1998. MAIN OUTCOME MEASURES: Seroprevalence and notifications were analysed by age, sex and State/Territory. RESULTS: 41.1% of serum samples were seropositive for hepatitis A (95% CI, 39.4%-42.9%) (population-weighted seroprevalence, 38.3%). Seroprevalence was significantly associated with increasing age (P<0.001), but did not differ between the sexes (male:female ratio, 1.04:1; 95% CI, 0.95-1.14). However, significantly more notifications were recorded for males than females (male:female ratio, 1.65:1; 95% CI, 1.60-1.70). The Northern Territory had the highest seroprevalence (68.8%; 95% CI, 52.7%-84.8%) and annual notification rates (48.7 per 100,000 population; 95% CI, 45.0-52.4 per 100,000). CONCLUSIONS: These data show that about half the Australian population has not been exposed to hepatitis A and is therefore susceptible to infection. However, any decision on national routine childhood hepatitis A vaccination requires a cost-benefit analysis. Routine vaccination of high-incidence communities remains controversial.

A randomized trial of two acellular pertussis vaccines (dTpa and pa) and a licensed diphtheria-tetanus vaccine (Td) in adults.

A single blinded randomized controlled trial to compare the reactogenicity and immunogenicity of adult formulated dTpa and monovalent pa vaccines with a licensed Td vaccine. Five hundred and forty-eight healthy adults aged 19-70 years received a single injection of dTpa or separate injections of pa or Td (with the alternate vaccine 1 month later). Local and systemic reactions were monitored for 15 days after each vaccination. Serum antibody levels were measured immediately prior to and 1 month after vaccination. Antibody levels were measured 12 months after vaccination in 100 subjects. There was no difference in the total frequency of symptoms and signs between subjects receiving any of the three vaccines. There was a significantly lower incidence of local reactions following pa (60%) than dTpa (80%, P=0.002) or Td (93%, P=0.0008). The incidence of clinically significant (Grade 2 or 3) swelling (> or =20 mm) was higher for Td (20%, P=0.002) than for dTpa (11%) or for pa (2%), however, there were no other significant differences in the incidence of Grade 2 or 3 reactions between the vaccines. A high anti-pertussis seroconversion rate (>97%) against all the studied pertussis antigens was seen 1 month after vaccination with dTpa and pa. A total of 96 and 99% of subjects receiving dTpa and Td, respectively, had anti-diphtheria titres > or =0.01 IU/ml, and all but one subject had anti-tetanus titres > or =0.1 IU/ml after 1 month. Twelve months after vaccination the majority (90-100%) of the subjects were still seropositive for each antigen and although GMTs had decreased they were substantially higher than pre-vaccination levels. The dTpa vaccine was well tolerated and capable of eliciting an immune response against all the antigens in a broad spectrum of the adult population and could potentially replace Td for routine boosters in adults.

Measuring immunisation coverage in Australia. A review of the Australian Childhood Immunisation Register.

BACKGROUND: Before the establishment of the Australian Childhood Immunisation Register (ACIR), measurement of childhood immunisation coverage in Australia involved a variety of methods at varying intervals by general practice (GP) divisions, state health departments and the Australian Bureau of Statistics. Such surveys may underestimate (child health records) or overestimate (parental recall) true immunisation coverage. OBJECTIVE: The establishment of the ACIR in 1996 (a world first), was a huge undertaking involving 15,000 immunisation providers (60% GPs) notifying over 3 million immunisations annually. This review summarises the operation of the ACIR, how it calculates coverage, the accuracy of estimates from the ACIR and how Australia's immunisation coverage compares with that of other similar countries. Currently, the accuracy of the records on the register is questioned, especially in urban areas, but available data suggest that failure to report to the ACIR is the main source of data discrepancies. DISCUSSION: The ACIR has the potential to measure immunisation coverage at any practice or local level with accuracy and timeliness. With full provider participation, the ACIR is capable of identifying areas of low immunisation coverage for targeted interventions and will play a key role in the current measles campaign, the General Practice Immunisation Incentives scheme and in payments to parents. Achieving the highest possible completeness and timeliness of the ACIR is in the interests of providers, consumers and health planners.

Parent and general practitioner preferences for infant immunisation. Reactogenicity or multiple injections?

AIM: To explore the relative importance parents and general practitioners place on less reactogenic vaccines and multiple injections at each childhood immunisation encounter. METHOD: A random sample of western Sydney parents (n = 162) and GPs (n = 154) completed telephone questionnaires about their preference for either a single injection of pentavalent vaccine (whole-cell pertussis/diphtheria/tetanus/Hib/hepatitis B), or regimen containing the less reactogenic acellular pertussis vaccine requiring two separate injections (acellular pertussis/diphtheria/tetanus and Hib or three separate injections (acellular pertussis/diphtheria/tetanus and Hib and hepatitis B). Potential confounders were examined by univariate and multivariate analysis. RESULTS: Regimens containing acellular pertussis vaccine (2 injections or 3 injections) were preferred by 72% and 58% of parents respectively. Those whose children were already vaccinated were less concerned about side effects and were twice (or = 2.0, 95% CI 1.0-4.0) as likely to select the pentavalent (single injection) option. 69% and 77% of GPs preferred the pentavalent rather than the two or three injection acellular option, although previous experience with a systemic adverse reaction to immunisation increased their preference for the acellular pertussis vaccine (or = 2.9, 95% CI 1.1-7.6). Only 54% of parents and 28% of GPs favoured three injections at one visit. CONCLUSION: Parent and GP concerns regarding reactogenicity and multiple injections differ. Parents are more concerned about vaccine reactogenicity than multiple injections. However, if the GP recommends a particular regimen, it is likely to be accepted by parents.

Vaccination of children following a previous hypotonic-hyporesponsive episode.

BACKGROUND: Hypotonic-hyporesponsive episodes (HHE) were once considered a contraindication to pertussis vaccination. METHODOLOGY: To evaluate the safety of further vaccination, chart review was conducted of 66 children who had experienced an HHE, and who were assessed in one of three special clinics in three capital city tertiary paediatric hospitals. Immediately prior to the HHE, 63 children had received whole-cell pertussis vaccine, three had received acellular pertussis vaccine. RESULTS: Sixty-four of the 66 children were vaccinated in the special clinic, 59 with pertussis-containing vaccines (55 acellular, four whole-cell), without serious adverse events. There were no HHE after these further vaccinations. CONCLUSIONS: Previously healthy children who experience HHE reactions can safely continue standard vaccination schedules.

A statewide survey of general practitioners in NSW, Australia, about immunisation and strategies to increase childhood immunisation rates.

A statewide survey was conducted to ascertain GPs' views in New South Wales (NSW), Australia, about the potential usefulness of strategies to increase immunisation rates and to facilitate providing childhood immunisation in their practice. The survey also explored the usefulness of information sources about immunisation. From September 1997-January 1998, a cross-sectional study using a four page self-administered questionnaire was undertaken. Four hundred GPs practising in NSW, Australia were randomly selected and 343 were eligible to participate. Of these, 281 returned a completed questionnaire (82% response rate). Ninety-one percent and 88% of GPs, respectively, agreed that television campaigns or registering children with the national Australian Childhood Immunisation Register (ACIR) were likely to increase immunisation rates. Sixty-two percent of respondents considered that the media created unwarranted parental concern about immunisation. GPs most commonly rated availability of an ACIR list of children overdue for immunisation, better parent educational material and better access to vaccines as strategies which would make immunisation easier. Sixty percent of respondents felt that increased GP payments would be successful in increasing immunisation rates. Only 51% indicated that they had used the "Australian Immunisation Procedures Handbook 6th edition" (a national clinical practice guideline) in the previous month. This study identified GP support for many initiatives aimed at increasing immunisation rates in Australia although GPs were sceptical about the benefits of some programmes. Studies to monitor the impact of GP incentives on immunisation rates in populations and individual practices are underway. These will be useful in determining whether GPs' opinions found in our study correlate with practice in this regard.

The epidemiology of tuberculosis in New South Wales 1975-1995: the effects of immigration in a low prevalence population.

SETTING: New South Wales (NSW) is Australia's most populous state and is home to one third of the country's rapidly growing immigrant population. OBJECTIVE: To examine the effects of immigration upon the epidemiology of tuberculosis (TB) in a low prevalence population. DESIGN: A retrospective review of state TB surveillance data in NSW from 1975-1995. RESULTS: The crude notification rate for all active TB declined from 12.2 per 100000 population in 1975 to 5.2/100000 in 1986, after which the notification rate increased steadily to 7.6/100000 in 1995. Between 1975 and 1995, the proportion of all TB notifications occurring in overseas-born residents increased from 30% (178/601) to 79% (345/435). During this period, the proportion of new extra-pulmonary TB notifications increased from 13% (72/549) to 42% (171/405). Notifications amongst women increased from 31% (188/601) to 47% (218/462) of the total, while the median age at notification fell from 55 to 41 years. The pattern of TB disease has not changed for Australian-born cases, who are mostly elderly men with pulmonary disease. Multidrug-resistant TB remains uncommon (<1%), and co-infection with the human immunodeficiency virus (HIV) and TB has not emerged as a major problem (2% of notifications), but is poorly documented. CONCLUSION: TB has re-emerged in NSW predominantly because of increased immigration from high prevalence countries. The epidemiology of TB has become dominated by overseas-born notifications, and now younger adults are primarily affected. Enhancing the effectiveness of the TB screening procedures for immigrants is a priority. Information should be provided to all immigrants and to long-term visitors from countries of high TB prevalence regarding TB infection and the TB services available in Australia.

Environmental investigation of a legionellosis outbreak in western Sydney: the role of molecular profiling.

This investigation used DNA profiling in an attempt to identify the environmental source of a community outbreak of 11 cases of Legionnaires' disease. Nine of these cases were culture positive and a single strain (DNA profile) of Legionella pneumophila serogroup 1 was isolated from eight cases. Spot water samples were collected from 51 cooling towers implicated by case exposure histories; this same strain was isolated from four towers at three separate locations up to 6 km apart. None of these locations had been frequently implicated by case histories. Because we did not perform an analytic epidemiological investigation, we were unable to identify a single environmental source for the outbreak. It is also possible that this outbreak was multifocal. The use of molecular profiling should not overshadow the importance of epidemiological methods in these environmental investigations. More data is needed regarding the prevalence, distribution, and clinical significance (virulence) of environmental L. pneumophila strains. This would aid interpretation of molecular profiling used in investigations of community legionellosis outbreaks.

Measles control in Australia. Report of the Measles Control in Australia Workshop, 5 November 1997.

The proceedings of the Measles Control in Australia Workshop held on 5 November 1998 are presented in this report. Prompted by the possibility of a global elimination campaign in the near future the Workshop considered the factors involved in elimination of measles from Australia. Epidemiology, surveillance, laboratory diagnosis methods, mathematical modelling, and the cost and logistics were all addressed. Mass vaccination for all 2-18 year olds, and a routine 2-dose regimen with scheduled doses at 12 months and school entry were recommended. Intensified surveillance, based on a sensitive case definition and laboratory confirmation (measles specific IgM) of suspected cases was identified as a crucial component of the campaign. The continuation of high vaccination coverage for each of the two doses would be essential to maintain elimination once established.

Invasive Haemophilus influenzae type b disease in elderly nursing home residents: two related cases.

We investigated two fatal cases of invasive Haemophilus influenzae type b (Hib) infection in a community nursing home in western Sydney, Australia. Two elderly women had lived in the same room, and the onset of their illness was 5 days apart. Hib isolates from blood cultures showed identical profiles by pulsed field gel electrophoresis. These findings suggest that Hib infection was transmitted within this nursing home. Serious Hib disease may be underrecognized in this setting. Continued surveillance and serotyping of invasive H. influenzae disease is essential for identifying groups at increasing risk that may benefit from immunization against Hib.