Send to

Choose Destination
Hum Vaccin Immunother. 2019 Jun 11. doi: 10.1080/21645515.2019.1619402. [Epub ahead of print]

Assessment of population immunity to measles in Ontario, Canada: A Canadian Immunization Research Network (CIRN) Study.

Author information

a Public Health Ontario , Toronto , ON.
b University of Toronto , Toronto , ON.
c National Microbiology Laboratory, Public Health Agency of Canada , Winnipeg , MB.
d University of Manitoba , Winnipeg , MB.
e Nova Scotia Health Authority , Halifax , NS.
f Canadian Center for Vaccinology, IWK Health Centre , Halifax , NS.
g Dalhousie University , Halifax , NS.
h Institute for Clinical Evaluative Sciences , Toronto , ON.
i Université Laval , Québec City , QC.
j Mount Sinai Hospital , Toronto , ON.
k Laboratoire de santé publique du Québec/Institut national de santé publique du Québec , Sainte-Anne-de-Bellevue , QC.
l McGill University , Montreal , QC.


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 titres above the threshold of protection (odds ratio = 1.60, 95% CI 1.14, 2.24). Most of the study cohort was 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 correlate of protection may not be an appropriate measure of population protection in measles-eliminated settings.


Canada; Measles; Ontario; herd immunity; measles immunity; sero-epidemiology; threshold of protection

Supplemental Content

Full text links

Icon for Taylor & Francis
Loading ...
Support Center