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A comparison of two pertussis epidemics in Auckland
Insights
The 1984 pertussis vaccine dose significantly reduced pertussis hospitalizations in Maori and Pacific Islander children by 1991. This study highlights the vaccine
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Public Health Epidemiology
Background:
- Pertussis (whooping cough) poses a significant health burden, particularly for indigenous populations.
- Previous pertussis epidemics in Auckland showed disproportionately higher hospitalization rates among Maori and Pacific Islander children.
Purpose of the Study:
- To evaluate the impact of the 1984 pertussis vaccine dose on hospitalization rates.
- To assess changes in pertussis hospitalization rates for Maori and Pacific Islander children following the vaccine introduction.
Main Methods:
- A population-based retrospective chart review compared pertussis hospitalizations in children (0-14 years) during the 1991 epidemic to data from the 1982 epidemic.
- Hospitalization rates were calculated per 1000 children using census data, with relative risks (RR) comparing 1991 to 1982.
Main Results:
- Overall pertussis hospitalizations decreased significantly from 1982 to 1991 (RR=0.43).
- Maori children experienced a substantial reduction in hospitalization rates (RR=0.26), as did Pacific Islander children (RR=0.29).
- Other/European children showed no significant change in hospitalization rates (RR=0.91).
Conclusions:
- The 1984 pertussis vaccine dose was associated with a significant reduction in pertussis hospitalizations.
- This reduction was primarily driven by decreased hospitalization rates among Maori and Pacific Islander children, indicating improved vaccine effectiveness or uptake in these groups.
Aim:
To determine if the addition of the 6 week dose of pertussis vaccine in 1984 was associated with any change in the hospitalisation rate for children with pertussis and the higher hospitalisation rates for Maori and Pacific Islander children with pertussis.
Design:
Population based study of pertussis hospitalisations using a retrospective chart review of hospitalisation data for children during the 1991 epidemic, which was compared to previously published data from the 1982 epidemic.
Setting:
Princess Mary and Middlemore hospitals, Auckland.
Subjects:
Children aged 0-14 years resident in metropolitan Auckland and hospitalised in Auckland during 1982 or 1991 with pertussis.
Measurements:
Hospitalisation rates were calculated as number of children with a discharge diagnosis of pertussis per 1000 children aged 0-14 years based on 1981 and 1991 census data. 1982 data were converted to person-years as published report was for an 8 month period. Hospitalisation rates were compared as a relative risk (RR) of hospitalisation in 1991 versus 1982.
Results:
There were 84 cases during 8 months in 1982 and 66 cases in 1991. Rates of hospitalisation by ethnic group; in 1982 were 0.24 Other/European (OE), 1.98 Maori (M), 1.37 Pacific Islander (PI); and in 1991 were 0.22 OE, 0.51 M, 0.40 PI. Compared to 1982 the relative risk of hospitalisation in 1991 adjusted for ethnicity was 0.43 (CI 0.33, 0.58, p < 0.0001). Compared to 1982 there was a significant reduction in the hospitalisation rate in 1991 for M (RR = 0.26, CI 0.16, 0.43, p < 0.0001); and PI children (RR = 0.29, CI 0.16, 0.54, p < 0.0001); but not for OE children (RR = 0.91, 95% CI 0.57, 1.46, p = 0.70).
Conclusions:
There was a significant reduction in the rate of hospitalisation for pertussis in 1991 compared to 1982. This reduction in hospitalisation rate was due to a reduction in rates for Maori and Pacific Islander children.