JMIR Publications

ABSTRACT

Background:

Evidence supporting declining trend of third wave of coronavirus disease-2019 (COVID-19) incidence is mounting, yet variants of concern (VOCs) continue to pose public health challenge in Canada. The emergence of VOCs has sparked discussions on how to effectively control their impacts on population.

Objective:

As provincial and territorial governments are at different levels of implementation of policy measures to protect people against community transmission of COVID-19, few research has examined the impact of policy countermeasures on the VOCs in Canada. Our objective was therefore to identify provinces with disproportionate prevalence of VOCs relative to COVID-19 mitigation efforts in provinces and territories in Canada.

Methods:

We analyzed publicly available provincial- and territorial-level data on the prevalence of VOCs in relation to mitigating factors (summarized in three measures: 1. strength of public health countermeasures: stringency index, 2. how much people moved about outside their homes: mobility index, and 3. vaccine intervention: proportion of Canadian population fully vaccinated). Using spatial agglomerative hierarchical cluster analysis (unsupervised machine learning), the provinces and territories were grouped into clusters by stringency index, mobility index and full vaccine coverage. Kruskal-Wallis test was used to determine the differences in the prevalence of VOC (Alpha, or B.1.1.7, Beta, or B.1.351, Gamma, or P.1, and Delta, or B.1.617.2 variants) between the clusters.

Results:

Three clusters of vaccine uptake and countermeasures were identified. Cluster 1 consisted of the three Canadian territories, and characterized by higher degree of vaccine deployment and lesser degree of countermeasures. Cluster 2 (located in Central Canada and Atlantic region) was typified by lesser implementation of vaccine deployment and moderate countermeasures. The third cluster was formed by provinces in the Pacific region, Central Canada, and Prairie region, with moderate vaccine deployment but stronger countermeasures. The overall and variant-specific prevalence were significantly different across the clusters.

Conclusions:

This ‘up to the point’ analysis found that implementation of COVID-19 public health measures including mass full vaccination of populations are key to controlling VOC prevalence rates in Canada. As of June 15, 2021, the third wave of COVID-19 in Canada shows a declining trend, and those provinces and territories that had more comprehensive public health stringency measures correlated with lower VOC prevalence. Public health authorities and governments need to continue to communicate the importance of socio-behavioural preventive measures even as populations in Canada continue to receive their full dose of vaccines. Clinical Trial: Not applicable.