OTTAWA — Manitobans had the highest rate of COVID-19 antibodies in January, in an ongoing survey of blood donors that could shed light on how long immunity lasts.
"It’s not the sole reflection of what is going on in the community," said McGill University public health professor Dr. Catherine Hankins.
"It’s a little bit of a canary in the coal mine."
Hankins co-chairs the national COVID-19 immunity task force, which uses various means to figure out how many Canadians got infected with COVID-19 without knowing it, as well as how the body fights off the coronavirus.
One of those projects involves screening samples collected by Canadian Blood Services for antibodies, which the body starts producing as someone recovers from COVID-19, because the immune system has been trained to attack the coronavirus.
In February, Hankins’ team released its survey of November 2020 blood samples collected outside of Quebec, and found 8.56 per cent of the 380 Manitoba samples contained antibodies to COVID-19, compared with 1.51 per cent nationally.
Now, more recent data show that among January donations, 3.92 per cent of 1,325 Manitoba donors had antibodies to COVID-19, compared with 1.99 per cent nationally.
Manitobans had the most antibodies of the nine provinces studied in November and January.
Meanwhile, Winnipeg blood samples collected in January showed 2.46 per cent contained COVID-19 antibodies. That’s a significant increase from the 1.77 per cent recorded in November 2020 — but lower than the rate of antibodies detected in Calgary and Edmonton in January.
That generally matched the epidemiological picture of how the second wave hit the Prairies.
Hankins’ team is processing samples from 48,000 testing kits mailed out to homes across Canada. The goal is to determine how many Canadians contracted the coronavirus without knowing it. More than 3,630 of such tests were sent to Manitoba.
Hankins said the national response rate is at least 25 per cent, and the results will probably give Manitobans a better idea of whether far more people got COVID-19 than those who got tested.
As for the January blood-sample survey, Canadian Blood Services noted that people who self-identified as white and those living in richer neighbourhoods were significantly less likely to have COVID-19 antibodies.
The January samples date back to before there was widespread vaccination and when more transmissible variants hadn’t taken hold.
"Things are moving so quickly that January results really don’t reflect what’s happening right now in Manitoba," said Hankins.
She said Manitoba’s case counts, vaccination rate and the ability to do contact tracing can paint a more immediate picture of how COVID-19 is spreading.
"Those variants, once they get circulating, they move quickly if the conditions are ripe," she said.
As with the previous blood-donation report, one of the highest rates of antibodies in Canada was in the region that includes Thompson, Island Lake and Norway House, known as "north-central Manitoba," where 15.2 per cent of 88 donors had antibodies in January.
Despite the smaller sample size, the margin of error suggests the result is statistically significant.
Hankins praised the "innovative" approach Manitoba has taken to roll out vaccines to all adults in the province’s north, to protect the most remote communities.