Table 4. Pan American Health Organization essential criteria for the verification of measles elimination.
| Criterion | Indicator | Description |
|---|---|---|
| Verify the interruption of endemic measles cases for a period of at least three years from the last known endemic case, in the presence of high-quality surveillance. | Zero cases of endemic transmission. | Criterion met. Canada achieved measles elimination status in 1998. Since then, molecular and epidemiological data continue to demonstrate that no viral strain has circulated for a period of one year or more in Canada (6,20,21,22). |
| Maintain high-quality surveillance sensitive enough to detect imported and import-related cases. | > 2 suspect cases per 100,000 population adequately investigated. | Criterion partially met. As only confirmed cases of measles are nationally notifiable in Canada, this indicator cannot be directly assessed. However, using data obtained by the Measles and Rubella Surveillance (MARS) pilot project, the national rate of measles-like illness investigation was estimated to be between 12 per 100,000 population (2006, non-outbreak year) and 19 per 100,000 population (2011, outbreak year) (23). |
| Verify the absence of endemic measles virus strains through viral surveillance. | Measles genotype assessed in 80% of outbreaks. | Criterion met. Genotype information was available for 100% of outbreaks reported in 2015. |
| Verify adequate immunization in the population. | 95% of population cohorts aged 1 to 40 years have received a measles-containing vaccine. | Criterion not met. As a national immunization registry does not currently exist in Canada, this criterion cannot be directly assessed. However, the 2013 Childhood National Immunization Coverage survey estimated first dose measles-containing vaccine coverage among two year olds to be 89.6% and second dose measles-containing vaccine coverage among seven year olds to be 85.5% (24). This estimate reflects a change in methodology, as opposed to a decline in coverage, from previous years (e.g., 95.2% and 94.9%, 2011 (25)). Note that these are average values; coverage is heterogeneous and will be higher in some areas and lower in others. |