Public health officials urge vigilance as new strains emerge
Variant identified in South Africa confirmed in Mississauga man who had not travelled
With accelerating transmission of one dangerous coronavirus variant and the province’s first identification of a different, potentially more worrying one, public health officials warn that any relaxation of COVID-19 controls could plunge Ontario into a third wave of the pandemic just as the second wave has begun to recede.
Ontario’s first known case of a
“variant of concern” initially identified in South Africa was confirmed Monday in a Mississauga man who had not travelled, according to Peel Public
Health. Scientists worldwide are urgently studying this variant, known scientifically as
B.1.351, because emerging evidence shows it carries mutations that help the virus evade immune defences and diminish the potency of vaccines.
Transmission of another variant first identified in the U.K., known as B.1.1.7, showed troubling signs of accelerating in parts of the province. York Region reported 39 cases of the extra-contagious variant, up from 15 last Monday — more than doubling in the span of a week. The majority of those cases were acquired locally, in people who had
not travelled.
And in Toronto, a large outbreak at a meat production facility was linked to B.1.1.7. Two individuals among a cluster of 78 COVID-19 cases at Belmont Meats screened positive for the variant; no one involved in the outbreak has recently travelled or had contact with anyone who travelled, according to Toronto Public Health.
Ontario now has 69 confirmed variant cases as of Sunday, up from 34 a week ago, according to data from Public Health Ontario. Officials warned last week that community spread of B.1.1.7 was underway, and that the variant — which researchers have calculated is about 50 per cent more transmissible than older versions — could become the dominant strain in the province by March.
Officials and experts emphasized that the existing toolbox of public health measures will still work against the new versions of the virus, and that approved vaccines are still likely to be effective — but that the threat posed by new variants requires heightened vigilance, with little room for error.
Dr. Karim Kurji, medical officer of health for York Region, noted that dropping case counts in Ontario could quickly be overwhelmed by rising incidence of B.1.1.7.
“I don’t like to say that that will happen. But if it does happen, then we may well be into the third wave of the pandemic,” Kurji said Monday, warning that the third wave could be worse than the second.
“The concern now becomes that the variants are circulating in the community,” said Dr. Lawrence Loh, medical officer of health for Peel Region, calling the province’s situation “precarious.”
“It would be really quite a shame if we were to open too quickly, or increase contacts too quickly. That would give more transmissible variants of concern the opportunity to spread more widely and essentially erase the gains that we’ve made.”
Both the new variants, which originated in the U.K. and South Africa, along with a third variant of concern first identified in Brazil known as P.1, share a mutation in a key region of the virus’s spike protein. Scientists believe this mutation, in combination with others, makes the variants better at clinging onto receptors on our cells, heightening transmissibility.
In addition, the B1.1.7 and B.1.351 variants share another mutation that appears to help the virus escape some of the immune defences mounted by people who are vaccinated or who were already infected with COVID-19 and have since recovered.
In studies using blood drawn from people vaccinated with the Moderna vaccine, one of two vaccines approved for use in Canada, scientists found a sixfold reduction in the power of neutralizing antibodies against the B.1.351 variant, but no change in the shot’s efficacy against the B.11.7 variant. Moderna said the vaccine still offered protection against B.1.351, but the company would advance work on a booster shot for emerging variants.
A more limited study by Pfizer also showed slightly reduced, but still protective, efficacy against B.1.351.
Novavax, whose vaccine is currently under review for approval by Health Canada, reported last week that its shot offered 86 per cent efficacy against the U.K. variant but only 60 percent in the South African arm of its trial, where B.1.351 dominates — still effective, but significantly less so. Data from the trial also bolstered reports of reinfection.
Other countries, including the U.K. and Denmark, have still managed to wrestle their winter waves into submission even as incidence of the variants spiked.
Last week, however, officials suggested that Ontario’s reproduction number — the average number of new cases generated by each infected person — should be below 0.7 to withstand the rise of B.1.1.7. Ontario’s reproduction number is currently above 0.8.
“The same control measures apply, and they work for the new variants,” said Dr. David Fisman, an epidemiologist at the University of Toronto’s Dalla Lana School of Public Health and a member of the province’s COVID-19 Science Advisory Table. “It’s just you have a less margin for error with these things, because they are more transmissible.
“So you have to do the same stuff, but you have to do it a bit better than you did before.”