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Effectiveness of a whole cell pertussis vaccine in child-care centers and schools
G De Serres1, N Boulianne, B Duval
1Centre de Santé Publique de Québec, Beauport, Canada.
Insights
Pertussis vaccine effectiveness may be lower than expected, potentially contributing to increased pertussis cases in Quebec. High vaccine coverage in child-care centers and schools was observed.
Area of Science:
- Public Health
- Epidemiology
- Vaccinology
Background:
- Pertussis (whooping cough) incidence has significantly risen in Quebec, Canada, since 1990.
- Investigating vaccine effectiveness and coverage is crucial for understanding and controlling pertussis outbreaks.
Purpose of the Study:
- To estimate the effectiveness of the pertussis vaccine.
- To assess pertussis vaccine coverage in child-care centers and elementary schools in Quebec.
Main Methods:
- Conducted two retrospective cohort studies involving 4482 children in child-care centers and 3429 pupils in elementary schools.
- Assessed pertussis symptoms via questionnaires and medical records; immunization status confirmed through written records.
Main Results:
- Vaccine coverage was high: ≥3 doses for 95% in child-care centers and ≥4 doses for >98% in schools.
- With ≥4 doses and a standard case definition, pertussis vaccine effectiveness was 60-61%.
- Using a stricter case definition (cough >5 weeks), effectiveness increased to 71-86%.
Conclusions:
- The rise in pertussis in Quebec is unlikely due to low vaccine coverage.
- Reduced vaccine effectiveness may be a contributing factor to the recent increase in pertussis cases.
Background:
Pertussis has substantially increased in Quebec, Canada, since 1990. We estimated pertussis vaccine effectiveness and vaccine coverage in child-care centers and elementary schools.
Methods:
Two retrospective cohort studies were simultaneously conducted. One included 4482 children attending 88 public child-care centers and the other included 3429 pupils in 14 elementary schools. Cough and pertussis symptoms were assessed through a questionnaire and medical records; immunization status was ascertained by examination of written records.
Results:
In child-care centers 95% of children had received at least three vaccine doses at the beginning of the follow-up; in schools more than 98% of pupils had received at least 4 doses. With > or = 4 doses of vaccine and a standard case definition used for surveillance (cough > or = 2 weeks, > or = 1 pertussis symptom and no other apparent cause for cough), vaccine effectiveness was estimated at 61% (95% confidence interval, 44 to 72%) in child-care centers and at 60% (95% confidence interval, 10 to 82%) in schools. With the same number of doses but a case definition requiring a cough > or = 5 weeks, vaccine effectiveness increased to 71% (95% confidence interval, 49 to 83) in child-care centers and to 86% (95% confidence interval, 66 to 94%) in schools.
Conclusions:
The increase in pertussis in Quebec is not caused by a low vaccine coverage. A low vaccine effectiveness may contribute to the resurgence of pertussis in the past decade.