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The effect of an accelerated immunisation schedule on pertussis in England and Wales
J M White1, C K Fairley, D Owen
1Immunisation Division, PHLS Communicable Disease Surveillance Centre.
Insights
Pertussis (whooping cough) notifications significantly decreased in England and Wales following increased vaccination coverage. The whole cell pertussis vaccine demonstrated high efficacy, protecting children against this infectious disease.
Area of Science:
- Epidemiology
- Immunology
- Public Health
Background:
- Pertussis (whooping cough) notifications in England and Wales drastically declined between 1982 and 1994.
- This decrease coincided with rising pertussis vaccine coverage.
- Incidence reduction was observed across all age groups, including infants.
Purpose of the Study:
- To evaluate the efficacy of the current whole cell pertussis vaccine.
- To assess vaccine performance under an accelerated vaccination schedule implemented in 1990.
- To establish an enhanced surveillance system for monitoring pertussis cases.
Main Methods:
- An enhanced surveillance scheme was implemented in 1994.
- The scheme focused on laboratory-confirmed cases of pertussis.
- Data collection included age, vaccination status, and outcomes.
Main Results:
- Overall vaccine efficacy was 94% for children aged 6 months to 5 years.
- Vaccine efficacy was 89% for children aged over 5 and under 15 years.
- Three unvaccinated infants under 8 weeks of age died from confirmed pertussis.
Conclusions:
- The whole cell pertussis vaccine is highly effective under the accelerated schedule.
- The surveillance scheme provides valuable data for ongoing monitoring.
- Further evaluation of protection duration and disease impact is warranted.
Abstract:
Notifications of pertussis in England and Wales have fallen dramatically from 65 810 during the epidemic year of 1982 to 3963 cases during the epidemic year of 1994, as vaccine coverage has risen. The incidence of pertussis has declined in all ages, including babies under 3 months of age who would have been at risk of disease from older siblings vaccinated under the accelerated schedule introduced in 1990 if immunity induced as result of this schedule had been short lived. To document the efficacy of the current whole cell vaccine under the accelerated schedule an enhanced surveillance scheme based on laboratory confirmed cases of pertussis was set up in 1994. Three deaths occurred in infants with confirmed pertussis, all of whom were under 8 weeks of age and unvaccinated. The overall vaccine efficacy for those over 6 months and under 5 years of age was 94%. This estimate may be inflated, as a number of biases could lead to the underascertainment of cases in vaccinated children, but it is similar to previous estimates obtained for children of the same age vaccinated under the 3, 5, and 10 month schedule. Vaccine efficacy was 89% for children aged over 5 and under 15 years. The enhanced surveillance scheme will enable us to monitor the duration of protection under the accelerated schedule and evaluate the continuing impact of pertussis infection.