What does the “COVID season” really look like?

However, new highly contagious variants have emerged and are proliferating at various times around the world. Will we reach the regular “COVID season” in the near future?

Pandemics do not follow a clear pattern in Canada and the waves are hitting irregularly. Spring, autumn When winter Over the last two and a half years, it is mainly due to the removal of public health measures and new variants that threaten immunity from vaccines and previous infections.

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Also, various variants have been surprised at the country at unexpected times (sometimes completely missed), making it increasingly difficult to predict when and where the COVID wave will hit next. I am.

“To be honest, the virus is controlled here, not us,” said Michael, an infectious disease doctor, medical director of infection prevention and control at the Women’s College Hospital in Toronto, and CEO of HealthPEI. Dr. Gardam said.

“We are capricious when completely random evolutionary events occur, and it’s really hard to predict.”

Different countries, different waves

Canada Currently, there are nasty combinations of Omicron subvariants such as BA.1, BA.2, BA.2.12.1, BA.2.3, fueling the ongoing sixth wave after public health measures have been significantly lifted. Is supplying. 80 percent Vaccinated Canadians Half of the infected population..

The US avoided the main wave of BA.2 until the end of last month, BA.2.12.1 is now becoming the dominant stock Almost one-third of new cases, even in Europe Rapid increase in BA.2 subvariants Appearance with BA.4 and BA.5..

It is despite the relatively high vaccination rate Two-thirds are double vaccinated In the United States 70% or more In Europe, higher levels of previous infections.

As of February, more than half of Americans were infected with the virus, according to new data from. Centers for Disease Control and Preventionin the meantime EU authorities reported 60 to 80 percent of the European population is infected with COVID-19.

“Comparing countries will be more and more difficult … and to be honest, it was a bit difficult even before this,” said Deepta Bhattacharya, an immunologist at the University of Arizona.

“Alpha waves really nailed Britain, and it wasn’t really here, and I don’t know why. It was certainly introduced here, and it’s just as widespread. I didn’t, and I don’t know why. It’s like making it very difficult to understand and predict. “

Population immunity may slow future waves

Another factor that is difficult to predict is how the immunity of the population changes, and whether previous infections and high vaccination rates are protected or diminished over time.

Tuliode Oliveira, director of the Center for Epidemic Response and Innovation in South Africa, said South Africa has a high level of artificial immunity and it is estimated that more than 90% were previously infected, vaccinated, or both. ..

“That’s one of the reasons we believe that the big waves of Omicron we had didn’t lead to so many hospitalizations and deaths,” he said.

“And while BA.2 continues to dominate emerging infectious diseases in South Africa, it has not led to an increase in infectious diseases. This is in Europe, where the BA.1 wave is followed by BA.2. It was very different. Waves. “

The double blow of Omicron’s BA.1 and BA.2 also hit Canada hard, with a catastrophic fifth wave when BA.2 caused a small sixth wave in April at the end of last year. It fueled, but it pushed up the level of the population. Immunity.

“The more people infected and vaccinated with this, the better the feeling of weathering,” Gardam said.

“I hope every year we start to become like other coronaviruses that infect us and catch colds … and in the end, it’s the virus that comes up with something newer than ever before. It’s pretty difficult. “

As a result, Omicron and its subvariants are completely Changed Canada’s immune system Over the past few months.

Previously, Canada was more consistent with countries like South Korea due to high vaccination rates and previously low levels of infection, with many countries with relatively low COVID levels throughout the pandemic. rice field.

Thanks to Omicron, we were similar to countries with much higher levels of artificial immunity, such as South Africa and the United States, but they protected us with high immunization rates.

“That means that new and submutants of Omicron can emerge … this can lead to a relatively large number of infections, but the rate of hospitalization and mortality is low. It may not be expensive, “he said.

“Look at Wave 1. It was a very small wave, but there were many hospitalizations,” Gardam said. “Then, Omicron finally hit, and the proliferation of infections was insane, but the mortality rate wasn’t as high as it was in the previous wave, so it’s better to fight it off.”

See | Canadians urged to take COVID-19 booster shots to fight the sixth wave.

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All signs indicate that Canada is experiencing a sixth pandemic wave, Dr. Teresatam confirms. Her message to Canadians: Wear a mask and boost if qualified. 2:00

According to Gardam, the difference between states like Prince Edward Island and Ontario throughout the pandemic is Primorskaya. COVID zero With this approach, there has been little existing immunity for the past two years.

But when Omicron struck in December, it took advantage of the state’s lack of artificial immunity.

“It was like a bang, it’s here,” he said. “And it’s still passing through the population, and yet we’ve taken stricter steps than Ontario and other states have done, but they’ve gone through all these different waves we didn’t have.”

How do you reach the “COVID season” where variants are constantly emerging?

It is unclear whether high vaccination rates consistent with Canada’s newly discovered levels of artificial immunity will fend off future waves of the virus and approach seasonality, but more from other countries. There is an early hint that it may be possible to predict accurately.

Tom Wenselias, an evolutionary biologist at KU Ruben University in Belgium, said: twitter South Africa is beginning to show seasonal signs in COVID, which can look like “significant waves with significant mortality and morbidity every 6 months.”

“The impact on the healthcare system of both BA.2.12.1 and BA.4 and BA.5 is not yet clear. It will certainly cause a wave of infection, but the impact on expected hospitalization and mortality. Can’t be estimated yet. At this point. “

“Early data seem to suggest the same severity as the original Omicron in terms of case admission rates … but it’s really an early day to guess this.”

De Oliveira, who led a research team that identified subvariants BA.4 and BA.5 in South Africa, said weakened immunity from infection and vaccination could affect their spread.

“The only thing that can play a role in that is the timing of the BA.1 wave, so we’re looking at the data very carefully,” he said.

“We are talking about 3-4 months past the peak of BA.1 and we know that artificial immunity begins to decline in about 3-4 months.”

New preprint survey Although de Oliveira’s co-author, which has not yet been peer-reviewed, suggests that BA.4 and BA.5 have “growth benefits” over South Africa’s BA.2 and may cause another wave. , Whether it happens or not has not yet been seen there or in other countries.

And more variants are imminent.

“It seems to be the behavior of SARS-CoV-2 and I don’t think we should be shocked to see another variant,” said Allison Kelvin, a virologist at the Center for Vaccine Science and Vaccine Infectious Diseases, Canada. Says. In Saskatoon.

“But unfortunately, keep those plans going. I think this will affect our vaccination strategy … by the time you roll. [an updated vaccine] There are new variants. “

Canada’s chaotic COVID wave pattern has not yet shown a major sign of seasonality, but there are some signs we are heading towards it.

“There is still seasonality associated with COVID, which does not mean that it fits perfectly, but of course, more cases can be seen during the colder months of Canada,” said an infectious disease doctor. One Dr. Isaac Bogoch said. Toronto General Hospital.

“Hopefully this wave has subsided and there’s a great summer in front of us … but can it be confusing with a highly contagious variant? Maybe. That may be the case. ”

According to Gardam, COVID-19 is not possible to completely eliminate COVID-19 in the long run, as other viruses such as H1N1, the influenza strain that caused the 1918 pandemic, are not available. It is expected to be prevalent over the years. Causes somewhere near the same level of illness.

“Twenty years later, I have to assume that there is a wreckage of this coronavirus that we regularly infect around,” he said. “But that’s no longer a big deal.”