VANCOUVER -- A new study suggesting B.C. had low transmission of COVID-19 may be positive news, but could also mean problems if there are future waves of the virus, the province's top health officials said Thursday.
A joint study between the B.C. Centre for Disease Control, University of British Columbia, LifeLabs and public health scientists was released Wednesday and shows B.C.'s estimated overall infection rate is less than one per cent.
Provincial health officer Dr. Bonnie Henry and Dr. Danuta Skowronski, who was the lead researcher on the project, discussed some of the findings with media over the phone Thursday morning.
"Those conclusions (in the study) are a big bravo to British Columbians," Skowronksi said. "They signify success in our containment of (COVID-19). We effectively suppressed the community transmission of this virus."
The study, posted by health research website medRxiv, looked at anonymous blood samples that were collected in March and May for reasons unrelated to COVID-19.
The samples collected in March showed the virus was prevalent in 0.28 per cent of the samples. In the May samples, it appeared in 0.55 per cent.
Skowronski explained that using anonymous, non-voluntary samples was crucial.
"(Studies) that rely on people volunteering or being invited to participate, those will tend to have higher estimates because those were worried people for a reason in the first place that volunteered to be tested, whereas ours removed that element of self-selecting," she said.
But health officials cautioned there's concern with such low transmission rates: few people have immunity against the virus.
"We cannot rest on our laurels. We cannot assume that we are in the all-clear," Skowronski said.
"We do not have sufficient immunity in the population to prevent subsequent waves … we have a long way to go before we're there, which means it really comes down to the individual and collective measures of British Columbians to continue to keep this virus at bay."
The study also revealed that, when the prevalence is applied to the whole B.C. population, about 28,000 people may have been infected COVID-19. To date, 3,149 cases have been confirmed by health officials.
However, Henry said that discrepancy, which is about eight times higher, isn't surprising or unique to B.C.
"We know there was a period of time when we were not testing everybody because we didn't have the capacity to test everybody, so this primarily reflects that," she said.
"It reflects the period in March when we had our increasing numbers of community transmission, we had a lot of people coming back from travel … and we made them stay home, even if they had mild symptoms, because we did not have access to testing everywhere in the province."
Even so, Henry said it's not a reason to increase testing beyond what's now available.
"We do have an expanded access to testing right now," Henry said. "We are focusing our testing on making sure that anybody who has any symptoms … has access to a test that can be done anywhere in the province."
Both Skowronski and Henry said the study reinforced their understanding that testing asymptomatic people wouldn't be an effective use of resources.
"It would be very low yield at this point to test asymptomatic people without some other clear indication for it," Skowronski said.
With files from The Canadian Press
