Dispatch

Why are Canadian ICUs filling up faster than other countries?

An ambulance is shown outside a hospital in Montreal, Saturday, January 15, 2022. Graham Hughes/The Canadian Press.

The rapid spread of the Omicron variant and early research showing it is much less likely to cause severe outcomes than previous incarnations of the COVID-19 virus has left people around the world nervously eyeing the situation in nearby intensive care units, hoping for the best and fearing the worst.

Although Omicron may be less likely to send people to the ICU, some experts have warned that the highly transmissible virus could infect so many people that hospitals struggle to cope with the deluge of patients.

So far, the most sinister projections haven’t come to pass. In mid-December the Ontario COVID-19 Science Advisory Table predicted the province’s ICUs would see more than 600 occupants by the end of the year and, by mid-January, the hospitals still haven’t reported that many occupants.

In the United Kingdom, the ICU numbers have barely budged, with 11.4 people in ICU per million residents, even as Omicron cases reach dizzying heights. In Australia, they are at 15.2 per million people. In Canada? A spike starting in early January left the ICU occupancy rate at 27 occupants per million people on Jan. 13, the last day that all three countries reported reliable data.

The United States, which has always been in a league of its own on ICU occupancies, is at 76.7 per million.

The disparity between the United Kingdom and Canada stands out because until late December, the two countries were following an identical trendline. Australia has always been low and continues to be low, while the United States is high and continues to be high. The worst projections may not have panned out in Canada, but we are still seeing an ICU occupancy rate higher than countries with vaccination rates lower than us.

What’s causing the divergence? It’s almost impossible to say for sure, but there are a few theories that have been proposed.

Natural immunity levels

One stark difference between the U.K. and Canada over the two-year pandemic is the rate of infection.

Although officially reported case rates are likely massively underestimated due to the rapid speed of Omicron transmission, with at least nine in 10 cases going uncounted, the data from previous waves shows that about three times as many Britons endured a previous case of COVID-19 compared to Canadians.

That means the U.K. population is benefitting from a much higher level of natural immunity than Canada while the two countries face the Omicron wave. Because natural immunity offers longer lasting and stronger protection against symptomatic disease and hospitalization, it could make the difference in the ICUs.

“I strongly suspect the amount of post-infectious immunity in the unvaccinated cohort, and possibly levels of hybrid immunity is what makes the difference,” said Dr. Sumon Chakrabarti, an infectious diseases physician at Trillium Health Partners.

The Delta variant was still spreading

Another reason for Canada’s higher ICU occupancy rate could be the remnants of the more virulent Delta variant still circulating in late December. Although Omicron is now dominant, hospitalizations and deaths tend to lag infections by several weeks.

Rupa Subramanya, a columnist at the National Post, wrote that between Nov. 22 and Dec. 25, those with the Delta variant accounted for 190 ICU admissions or deaths in Ontario, while only eight were Omicron patients.

In British Columbia last week, many of the people in hospital were suffering from disease caused by the Delta variant, according to Dr. Bonnie Henry, the provincial health officer. Lingering Delta cases have also caused hospitalizations in New Brunswick.

Booster shots

When Omicron descended on the United Kingdom, Prime Minister Boris Johnson immediately called for an all-out blitz on booster shots. In terms of raw numbers, the plan worked: The U.K. has given more than 50 booster shots for every 100 residents.

Canada lags behind the U.K., with about 31 boosters given for every 100 residents and one-third of those shots coming in the last two weeks.

It’s possible that the booster gap made a small difference in the ICU occupancy rate of the two countries. Although Johnson’s booster campaign likely came too late to make much difference, since the shots take about a week or two to take effect, the U.K. had many more residents boosted on Dec. 1 than Canada did. A third shot has been shown to be very effective against symptomatic illness and severe effects from Omicron.

Omicron is not milder

Although there was a litany of evidence coming from South Africa, and other countries, that Omicron was less deadly than Delta it took some time for the world to be sure.

As late as Dec. 12, the director-general of the World Health Organization Tedros Adhanom said that it was “wrong for people to consider Omicron as mild.”

More recent research has definitively found that Omicron causes less severe disease and death than previous variants. A recent study out of California found that Omicron was half as likely to send people to hospital as Delta and that, out of 52,000 Omicron patients studied, not a single one needed a ventilator. This agrees with a handful of other studies from countries battling an Omicron wave.

Although federal modelling released on Friday still included a hypothetical scenario where Omicron turns out to be as severe as Delta — and some news organizations ran with that as the lead story — few believe that scenario is possible.

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