First serology test shows Covid-19 infection rate in Lower Mainland at 1%

Derek Kilbourn

Sounder News

Thursday, July 16 2020

A serology study, the first of it’s kind in Canada to have the findings released, has shown the infection rate of COVID-19 in the Lower Mainland to be less than 1 in 100 people.

That, according to Dr. Danuta Skowronski, an Epidemiologist, with BC Centre for Disease Control and Clinical Professor with the University of British Columbia who spoke to media on Thursday, July 16.

She was joined by Dr. Bonnie Henry, BC Provincial Health Officer and Minister Adrian Dix.

The sero-survey was done using a protocol established during the 2009 H1N1 pandemic, and was brushed off and made ready in January 2020 when it looked like there could be another pandemic about to happen.

Dr. Henry said, “we needed to have the protocols and ability set up to be able to do it, should the pandemic progress as it has, across the world.

“We are very lucky in that we have  number of researchers who do applied public health research. The protocol we have is based on validated protocol that was used for influenza - that helped us understand the 2009 pandemic in BC.

“We were able to rapidly put those same pieces in place to understand how COVID-19 has impacted our community.”

Dr. Skowronski explained the sampling for the study was done from 1,000 ‘sero’ samples taken from across the Lower Mainland, where the BC health officials expect infection rates are the highest.

“We can assume the provincial rates are lower than what we estimate.”

The samples represented all ages from 0 to 100 with proportional representation by age and sex.

The study partnered with Lifelabs, which is the only outpatient community based laboratory network serving the Lower Mainland - this allowed the researchers to get a representative snapshot of community residents.

Lifelabs provided, under the direction of Dr Henry anonymized sera leftover from other diagnostic testing.

As Dr. Skowronski explained, this meant there was a true representation of the community - rather than using a volunteer base to get samples.

She said based on the findings, fewer than 1 in 100 residents in the Lower Mainland were infected during the First Wave.

“First Wave mitigation measures in that regard were very effective. At a provincial level, community infection rates would have been even lower than that.”

Given that this data matched up with what is already shown through the Public Health case numbers and modelling, it once again showed BC has one of the lowest infection rates not only in Canada, but in North America.

Dr. Skowronski said, “a bravo to all British Columbians for successfully containing this.”

Dr. Henry said there are a number of studies going around, one of the key ones to do now is to look at the people who said yes to serology testing during the Covid-19 impact survey conducted by Public Health in May.

Dr. Henry said just under 400,000 people completed the survey and of those, roughly half said they would participate in serology testing.

She said, “what we need to do is target the groups that will give us information for who will be at more risk. Health care workers or [other] people working during the pandemic.”

Other sero studies will be looking at infection rates in children, as well as looking at rates of infection in blood samples taken from women who are pregnant.

Dr. Henry said, “we think there is some immunity, some protection, so if you are exposed again in the future, you might have a milder infection - but we don’t know yet, but that’s another piece of the puzzle that is not known and across the world.”

She added this study can’t answer how lon antibody protection could last, or whether this signifies complete protection.

“We do have other studies looking at how long lasting antibodies might be. This study does not address that.

“It does say, clearly, we do not have sufficient immunity in the population to prevent subsequent waves. It might not even be just a second wave, we might have undulations.

“We have a long way to go before we are there.

“It comes down to individual and collective measures of BCers to keep this virus at bay.”

Dr. Henry said our infection rates are low, “but even in places where they had a lot of infection, like Ne York and Italy, similar types of sero studies show the rates of infection are still way too low to allow for community immunity or prevention of other waves.”

Asked if knowing these numbers would have changed anything for the BC Covid-19 response, Dr. Henry said, “no. This reinforces the timing was good and we took the right measures.”

Dr. Skowronski said, “you want to prevent the exponential surge, the increase, you don’t want it to get out from under you like it has in other areas.

“We should applaud that what we did was so effective in preventing the community transmission that has happened in other areas.”