B.C. COVID-19 map: New data visualization shows vaccine impact across regions

The B.C. Centre for Disease Control has added a new chart to its COVID-19 Surveillance Dashboard that helps visualize the correlation between vaccination rates and infection rates in the province. 

The scatter plot shows each of the province's 89 local health areas, organized according to their vaccination rate and the number of cases per 100,000 residents recorded over the last three months, relative to the provincial average for both.

Between Sept. 9 and Dec. 9, the province saw 901 new COVID-19 infections per 100,000 residents, according to the graph. The proportion of fully vaccinated B.C. residents ages 12 and older is listed as 88 per cent, which is much closer to where the rate stood at the end of the three-month period than at the beginning.

Most regions of the province fit into one of two quadrants on the grid: They either have lower-than-average vaccination rates and higher-than-average cases, or they have higher-than-average vaccination rates and lower-than-average cases.

Sixty-seven of the 89 local health areas fit this pattern, reflecting the strong correlation between vaccination and lower rates of infection.

It should be noted that the three least populous local health areas in the province - Northern Health's Snow Country, Telegraph Creek and Stikine regions - are combined into a single group for the purposes of the BCCDC's surveillance dashboard, so there are functionally 87 regions, rather than 89.

Combined, those three regions have a below-average vaccination rate and an above-average infection rate, according to the dashboard. They're included among the 67 that fit the pattern.

The remaining 22 local health areas can be split into two categories: There are the lucky regions whose lower vaccination rates haven't translated into higher caseloads, and the unlucky regions that have seen higher-than-average caseloads despite above-average immunization.

There are more "lucky" regions than "unlucky" ones.

Seventeen local health areas have below-average immunization rates and below-average rates of infection. They are: Kootenay Lake, Nelson, Cowichan Valley West, Princeton, Castlegar, Greater Campbell River, Powell River, Haida Gwaii, Sunshine Coast, Oceanside, Southern Gulf Islands, Kimberley, Southern Okanagan, Summerland, Fernie, Comox Valley and Penticton.

Of this group, the Kootenay Lake and Powell River local health areas are the biggest outliers. Kootenay Lake has - by several percentage points - the lowest vaccination rate among the lucky local health areas.

Despite just 71 per cent of its residents ages 12 and older having had both shots, Kootenay Lake saw 339 cases per 100,000 during the three months in question. That's less than half the province-wide rate.

Powell River stands out in a different dimension. The region has a below-average vaccination rate of 83 per cent, but it recorded just 120 cases per 100,000 residents from Sept. 9 to Dec. 9. That's less than one-sixth of the provincial average, and the lowest per-capita case rate of any local health area in the province during that time period.

It's unclear why the 17 "lucky" regions have performed better than their vaccination rates suggest they should have.

They're located all around the province, with at least one in every health authority except for Fraser Health.

Larger numbers of them are located in the Interior and on Vancouver Island, and many of them are rural, remote, or both.

The Interior regions would have been under extra COVID-19 restrictions limiting the size of personal gatherings for most of the period shown on the graph, which could have helped keep case counts low. But other parts of the Interior were under the same restrictions and did not see lower-than-average case rates, and the only Northern Health region in the "lucky" group was Haida Gwaii, which was initially excluded from tighter restrictions imposed on that health authority.

The province lifted Interior-specific health restrictions late last month, and expanded Northern Health restrictions to the entire health authority at the same time. The Interior is still subject to province-wide rules, such as the mask mandate for indoor public spaces, and Northern Health's local rules are scheduled to expire on Jan. 31. 

The five "unlucky regions" with higher case rates than their vaccination rates suggest they should have are: Nisga'a, Kitimat, Howe Sound, Central Coast and Windermere.

These regions, too, are generally rural and remote, with the exception of Howe Sound, which is home to Whistler and Squamish and has by far the largest population of the five.

Nisga'a and Kitimat were among the regions initially excluded from Northern Health regional restrictions, while Windermere is in the Interior and was subject to the same restrictions as several of the "lucky" regions for most of the time period in question.