Effectiveness of a whole cell pertussis vaccine in child-care centers and schools.
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.
De Serres
G
G
Centre de Santé Publique de Québec, Beauport, Canada.
Boulianne
N
N
Duval
B
B
Déry
P
P
Rodriguez
A M
AM
Massé
R
R
Halperin
S
S
D002170:Canada; D002648:Child; D002656:Child Day Care Centers; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008499:Medical Records / Q000706:statistics & numerical data; D010567:Pertussis Vaccine / Q000008:administration & dosage / Q000276:immunology*; D012189:Retrospective Studies; D012574:Schools; D011795:Surveys and Questionnaires; D014917:Whooping Cough / Q000175:diagnosis / Q000276:immunology / Q000517:prevention & control
D010567:Pertussis Vaccine