Assessment of population immunity to measles in Ontario, Canada: a Canadian Immunization Research Network (CIRN) study.
Hum Vaccin Immunother
; 15(12): 2856-2864, 2019.
Article
in En
| MEDLINE
| ID: mdl-31184979
ABSTRACT
Canada eliminated measles in 1998. We conducted a sero-epidemiology study to estimate population immunity to measles in the province of Ontario, Canada and to identify groups at higher risk of outbreaks. We used a previously developed modified enzyme immunoassay to test 1,199 residual sera from patients aged 1-39 years. We re-tested negative and equivocal sera using a plaque reduction neutralization assay. We interpreted our results in the context of Ontario's immunization program and vaccine coverage data. Of 1,199 sera, 1035 (86.3%, 95% confidence interval (CI) 84.4, 88.2) were above the measles threshold for protection, 70 (5.8%, 95% CI 4.5, 7.2) were equivocal and 94 (7.8%, 95% CI 6.3, 9.4) were negative. The proportion of positive sera was highest for those 1-5 years, with 180/199 (90.5%, 95% CI 86.4, 94.5) positive sera, and lowest for those age 12-19 years, at 158/199 (79.4%, 95% CI 73.8, 85.0). Adjusted for age, females were more likely than males to have antibody titers above the threshold of protection (odds ratio = 1.60, 95% CI 1.14, 2.24). Most of the study cohort were eligible for two measles vaccine doses, and vaccine uptake in Ontario is >90% for school-aged cohorts. We observed a higher than expected proportion of sera with antibody levels below the threshold of protection, suggesting that immunity in some Ontario age-groups may be waning, despite high vaccine coverage. Alternatively, the traditional measles correlates of protection may not be an appropriate measure of population protection in measles-eliminated settings.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Immunization
/
Epidemiological Monitoring
/
Measles
/
Antibodies, Viral
Type of study:
Etiology_studies
/
Incidence_studies
/
Observational_studies
/
Prognostic_studies
/
Risk_factors_studies
/
Screening_studies
Limits:
Adolescent
/
Adult
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Child
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Child, preschool
/
Female
/
Humans
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Infant
/
Male
Language:
En
Journal:
Hum Vaccin Immunother
Year:
2019
Document type:
Article
Affiliation country: