Portal de Periódicos da CAPES

Assessment of population immunity to measles in Ontario, Canada: a Canadian Immunization Research Network (CIRN) study

2019; Taylor & Francis; Volume: 15; Issue: 12 Linguagem: Inglês

10.1080/21645515.2019.1619402

2164-554X

Shelly Bolotin, Alberto Severini, Todd F. Hatchette, Elizabeth McLachlan, Rachel Savage, Stephanie L. Hughes, John Wang, Shelley L. Deeks, Sarah E. Wilson, Marc Brisson, Scott A. Halperin, Jonathan B. Gubbay, Tony Mazzulli, Bouchra Serhir, Brian J. Ward, Natasha S. Crowcroft,

Zoonotic diseases and public health

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.