Measles vaccine efficacy during an outbreak in a highly vaccinated population: Incremental increase in protection with age at vaccination up to 18 months

During a large measles outbreak in Quebec City in 1989, two investigations conducted in parallel evaluated the relative risk of measles and measles vaccine effectiveness with respect to age at vaccination. The study was a school-based case-control study including 563 cases and 1126 classmate control...

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Bibliographic Details
Published in:Epidemiology and infection 1995-10, Vol.115 (2), p.315-323
Main Authors: De Serres, G., Boulianne, N., Meyer, F., Ward, B. J.
Format: Article
Language:English
Subjects:
Age Distribution
Age Factors
Antibodies
Case-Control Studies
Children
Cohort Studies
Disease Outbreaks
High schools
Humans
Infant
Maternal age
Measles
Measles - blood
Measles - epidemiology
Measles - immunology
Measles - prevention & control
Measles Vaccine - immunology
Measles vaccines
measles virus
Quebec - epidemiology
Risk
Seroepidemiologic Studies
Siblings
Urban Health
Vaccination
Viruses
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Summary:During a large measles outbreak in Quebec City in 1989, two investigations conducted in parallel evaluated the relative risk of measles and measles vaccine effectiveness with respect to age at vaccination. The study was a school-based case-control study including 563 cases and 1126 classmate controls. The second was a cohort study of the siblings of school cases including 493 siblings aged between 1 and 19 years. The relative risks (RR) of measles were similar in both settings and the trend towards increased vaccine efficacy with increasing age at vaccination was highly significant (P < 0·001). Vaccine efficacy rose from 85% in children vaccinated at 12 months of age to ≥ 94% in those vaccinated at 15 months and older. Even for children vaccinated at or after 18 months of age. the RR of measles was reduced when compared with children vaccinated between 15 and 17 months of age (RR 0·61. CI 95% 0·33–1·15). Small changes in the timing of initial measles vaccination can have a major impact on vaccine efficacy.
ISSN:0950-2688
1469-4409
DOI:10.1017/S0950268800058441