How Ontario's spike in 'delta variant' cases impacts fight against potential fourth wave

Ontario's science advisory table now estimates that nearly a quarter of all new COVID-19 cases in Ontario involve the so-called "delta variant" that was first detected in India.

Public Health Ontario has only been able to confirm 322 cases of the more infectious variant but because it has not designed a mass screening tool to easily detect cases and instead has to rely on conducting genomic sequencing on a limited number of samples, it is likely that some infections are slipping through the cracks.

On Wednesday the Ontario science advisory table updated its dashboard and estimated that the "Delta" variant now makes up about 23 per cent of Ontario's cases.

Over the last seven days, that would translate into more than new 200 cases of the variant each day.

The revelation comes in the wake of Peel Region's Medical Officer of Health Dr. Lawrence Loh telling reporters that the Delta variant could become the dominant strain in his community in one month “with the rest of Ontario weeks behind.”

“With initial signals suggesting that the Delta variant is also more transmissible and severe on top of the Alpha variant, this means we very much welcome the province’s continued cautious reopening as one component to preventing a fourth wave,” he said during a press conference in Brampton on Wednesday  morning.

The Delta variant was first detected in Ontario in late April.

While much is still unknown about the strain, recent studies conducted in England have suggested that it is more transmissible than the B.1.1.7 variant that is currently dominant in Ontario and and can cause more severe symptoms in younger adults.

In an interview with CP24 on Thursday morning, infectious disease specialist Dr. Isaac Bogoch said that the new variant is “already taking over” in the United Kingdom after being first detected in mid-April and is likely to do the same in Canada.

"The same rules of biology apply on both sides of the Atlantic. It is spreading here as well and it is outcompeting our other variants, mainly the B.1.1.7 variant," he said. "We have seen this play out before. We saw it when B.1.1.7 variant initially detected in the United Kingdom took hold in Canada and became the more dominant strain and now we are watching it again. But the big difference now is we are in the midst of a mass vaccine rollout and the best thing you can do in a situation like this is vaccinate as quickly as possible.'

There has been some research suggesting that the current COVID-19 vaccines are less effective against the Delta variant, though Bogoch said that it appears to be “predominantly spreading” in unvaccinated and partially vaccinated populations.

For that reason, he said that he continues to believe that Ontario “is in good shape” even if the strain eventually becomes dominant.

Nearly 70 per cent of Ontario adults have now received at least one dose of COVID-19 vaccine and the province has said that it hopes to have fully vaccinated everyone who wants to be by the end of the summer.

"Sometimes these are billed as races between the variant and the vaccine and we kept hearing that during for example the prior wave with B.1.1.7 but that variant was going to win every time. We just did not have that degree of vaccine coverage and community protection when that happened," he said.

"Now it is a completely different story. We are well ahead. We have vaccinated close to 70 per cent of the adult population in much of Ontario. There is a ways to go and certainly we have to gets second doses in but given the pace of vaccination and the uptake I think we are in good shape."