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A measles epidemic controlled by immunisation
Insights
The 1997 measles-mumps-rubella (MMR) vaccination campaign successfully prevented 90-95% of predicted measles cases. This public health intervention was highly effective in controlling the measles epidemic, particularly among children aged 10 and under.
Area of Science:
- Epidemiology
- Public Health
- Immunisation Science
Background:
- A measles epidemic was predicted in 1997, necessitating a planned immunisation campaign.
- The measles-mumps-rubella (MMR) vaccine campaign was targeted at children aged 2-10 years.
- The epidemic commenced prior to the planned vaccination drive.
Purpose of the Study:
- To describe the 1997 measles epidemic and its characteristics.
- To evaluate the impact of the MMR vaccination campaign on measles incidence.
- To assess the effectiveness of the targeted immunisation strategy.
Main Methods:
- Data integration from measles hospitalisation, notification, and laboratory records.
- Analysis of epidemic timeline, case numbers, hospitalisations, and mortality.
- Calculation of age-standardised incidence and hospitalisation rates across different ethnic groups.
Main Results:
- The epidemic spanned April 1997 to January 1998, with 2,169 identified measles cases.
- Measles incidence and hospitalisation rates were significantly higher among Pacific people and Maori compared to Europeans.
- Incidence was highest in infants under one year, with children aged 10 and under driving transmission.
Conclusions:
- The MMR vaccination campaign averted 90-95% of predicted measles cases.
- The campaign's targeting of children aged 10 and under was appropriate and effective.
- The study highlights the importance of timely and well-targeted immunisation programs in controlling infectious disease outbreaks.
Aim:
In 1997, an immunisation campaign, using measles-mumps-rubella vaccine, was planned for children aged 2-10 years to prevent a measles epidemic predicted by mathematical modelling. The epidemic started before the campaign and is described here.
Method:
Measles hospitalisation, notification and laboratory data were combined.
Results:
The epidemic started in April 1997 and was largely over by January 1998. No deaths were identified and only one hospitalisation was coded as measles encephalitis, compared to seven deaths and ten cases of measles encephalitis in the 1991 epidemic. For the 12 months from 1 March 1997 there were 2,169 (60 per 100,000) measles cases identified, 314 (9 per 100,000) of whom were hospitalised. Two-thirds of hospitalised cases were notified. The age-standardised measles incidence rates were 33, 34, and 174 per 100,000 for Europeans, Maori and Pacific people, respectively. The respective age-standardised hospitalisation rates were 4, 9 and 32 per 100,000. Measles incidence was highest for under one-year-olds (904 per 100,000) and low for 11-16 year-olds (27 per 100,000)--the cohort previously offered a second vaccine dose. Most cases were aged 10 years and under, and this group were the main drivers of virus transmission.
Conclusions:
The immunisation campaign prevented 90-95% of predicted cases. The campaign was appropriately targeted at children aged 10 years and under.