COVID-19 variants: Screening ramping up in B.C. over concerns of fast spread
Published Wednesday, January 27, 2021 6:48AM PST
A woman wears a protective face mask to help prevent the spread of COVID-19 as they walk past the emergency department of the Vancouver General Hospital in Vancouver Wednesday, Nov. 18, 2020. (Jonathan Hayward / THE CANADIAN PRESS)
VANCOUVER -- There's a race between COVID-19 and the rollout of vaccine as researchers and health officials in B.C. warn of two faster-spreading variants.
The number of variant cases may start low, but increased transmission could only be a few weeks away, just as delivery of the Pfizer-BioNTech vaccine is delayed, said Caroline Colijn, the Canada 150 Research Chair in Mathematics for Infection, Evolution and Public Health at Simon Fraser University.
Colijn's lab released modelling data this week showing public health rules in several provinces, including B.C., would not be sufficient to prevent exponential growth in cases starting around March if a COVID-19 variant with a 40 per cent higher transmission rate became established.
“By established I mean some cluster doesn't get stopped and takes off and we don't notice or we don't act and we are unable to stop those chains of transmission and so they take off the way the current COVID has,” she said.
Colijn added she would expect public health officials to enact further restrictions before such exponential growth in variant cases.
Provincial health officer Dr. Bonnie Henry told a news briefing this week that B.C. has detected three cases of a variant found in South Africa and none were linked to each other or to travel, pointing to community spread.
By completing whole genome sequencing, the B.C. Centre for Disease Control has also recorded six travel-related cases of the COVID-19 variant first found in the United Kingdom, which appears significantly more transmissible than earlier strains of the new coronavirus.
B.C. is sequencing about 15 per cent of samples that test positive for COVID-19 in the province, said Natalie Prystajecky, head of the environmental microbiology program at the centre's public health lab.
Sequencing is more labour-intensive than diagnostic testing, she said, so it can take up to two weeks to produce data from a given sample.
B.C. has sequenced about 11,000 COVID-positive samples since last February and generated quality data from about 9,500 of them, she said.
The average rate of sequencing across Canada is between five and 10 per cent, said Prystajecky, a member of the Canadian COVID-19 Genomics Network that received funding last spring to sequence 150,000 samples.
In addition to targeting samples from travellers and youth, she said, B.C. is prioritizing more general, “background” sampling to understand if public health officials are missing anything, such as transmission of new variants.
“We're ramping up,” she said. “We did 750 genomes last week and we're aiming to continue to increase the amount of sequencing we're doing.”
Prystajecky said her lab is also planning to do a “point prevalence study” to screen a high number of samples at a given point in time.
B.C. is taking a smart approach to sequencing by targeting travel-related cases, said Colijn, but at the rate sequencing data becomes available, “there could be 10 or 50 or 100 cases of whatever we detect at the time.”
Colijn believes B.C. should consider Atlantic Canada's approach and create a so-called “Pacific bubble” that would require travellers from other provinces to self-isolate for 14 days upon arrival in B.C.
Data from Pfizer and Moderna - the pharmaceutical companies behind the two COVID-19 vaccines approved in Canada - show their products still protect people against the U.K. and South African variants, said Fiona Brinkman, a professor in the molecular biology and biochemistry department at Simon Fraser University.
“What this means is people really need to hunker down until this vaccine gets out into the population further,” she said in an interview this week.
“We really are in a race between the vaccine and the virus right now.”
Basic measures including physical distancing and avoiding non-essential travel are still effective in preventing new variants from spreading, she said.
B.C. reported 4,260 active cases of COVID-19 on Tuesday out of more than 65,000 confirmed cases since the pandemic began.
This report by The Canadian Press was first published Jan. 27, 2021.
This story was produced with the financial assistance of the Facebook and Canadian Press News Fellowship.