As the COVID-19 wave after wave crashes on us, the hope is that we will eventually reach a point where the seasonality of the virus will make the pandemic easier to predict and eliminate. But with the highly contagious new variants emerging and leading to increases around the world at different times – will we soon reach a normal “COVID era”? The pandemic did not follow a clear pattern in Canada, with waves crashing into the country. spring, fall and winter the last two and a half years, largely due to the lifting of public health measures and new variants that threaten immunity to vaccines and previous infections. Different variants have also captured countries at unexpected times (and sometimes lost them completely), making it increasingly difficult to predict when and where COVID waves will hit. “Let’s be honest, the virus is in control here, not us,” said Dr. Michael Gardam, an infectious disease specialist, medical director of infection prevention and control at Women’s College Hospital in Toronto and CEO of Health PEI. “We are completely in the whim of any random evolutionary events happening and it is really difficult to predict.”
Different countries, different waves
Canada currently has an unpleasant combination of Omicron variants – including BA.1, BA.2, BA.2.12.1 and BA.2.3 – that fuel a continuing sixth wave after the lifting of public health measures, despite the fact that More than 80 percent of Canadians have been vaccinated and almost half of the population has been infected. The US avoided a big BA.2 wave until the end of last month, but BA.2.12.1 quickly becomes the dominant strain in almost a third of new cases, while Europe also faces a wave in the BA.2 variations and its appearance BA.4 and BA.5. This is despite the relatively high vaccination rates, with a little more two thirds double vaccinated in the US and more than 70 percent in Europe, and even higher levels of previous infection. More than half of Americans have been infected with the virus since February, according to new data from the US Centers for Disease Control and Preventionwhile said EU officials between 60 and 80 percent of the European population are infected with COVID-19. “It will become increasingly difficult to compare countries; and honestly even before that it was a bit difficult,” said Deepta Bhattacharya, an immunologist at the University of Arizona. “Alpha wave really nailed the UK and it was not really here and I do not know why it is. It was definitely introduced here and it did not spread to the same extent and I have no idea why. So there are all kinds of things that make it very difficult to understand and predict ». People are walking in the Chinatown neighborhood of Toronto in March 2021. Currently, Canada has an nasty mix of Omicron variants that feeds an ongoing sixth wave following the lifting of public health measures. (Evan Mitsui / CBC)
The population’s immunity could attenuate future waves
Another factor that is difficult to predict is how the population’s immunity will change – and whether previous infections and high vaccination rates will protect or weaken over time. Tulio de Oliveira, director of the South Africa Epidemic and Innovation Center, said South Africa had a high level of population immunity with more than 90% estimated to have been infected in the past, vaccinated or both. “This is one of the reasons why we believe that the big wave of Omicron we had did not translate into a very large number of illnesses and deaths,” he said. “And BA.2, despite appearing and continuing to dominate all infections in South Africa, did not translate into an increase in infection, which was very different in Europe, where they had a BA.1 wave followed by a BA .2 wave. “ This double collision of Omicron’s BA.1 and BA.2 also hit Canada hard, fueling a catastrophic fifth wave late last year that receded as BA.2 triggered a smaller sixth wave in April – but also raised levels. of our population immunity, immunity. “It gives you the feeling that the more people who are infected and vaccinated, the better you can deal with it,” Gardam said. “The hope is that it starts to become like the other coronaviruses that infect us every year and cause colds; and in the end it is very difficult for the virus to find something so original that you have never seen part of it.” As a result, the Omicron and its variants completely changed the landscape of Canada’s immunity the last months. Previously, Canada was more in line with a country like South Korea given its high vaccination rates and previous low levels of previous infection, de Oliveira said, with much of the country seeing relatively low COVID levels throughout the pandemic. . With Omicron, we looked more like countries like South Africa and the US with much higher levels of population immunity – but the high vaccination rate protected us. “This means that, as potentially new variants and sub-variants of Omicron. Emerge that can translate into a relatively high number of infections, but potentially not into a very high morbidity and mortality rate,” he said. “Look at the first wave, it was a very small wave, but there were a lot of treatments,” Gardam said. “Then the Omicron finally hit and the rise in infections was insane, but the mortality rate has never been as high as in previous waves. So we are getting better at fighting it.” CLOCKS Canadians urged to receive COVID-19 booster vaccines to fight the 6th wave:
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Gardam said the difference between provinces such as Prince Edward Island and Ontario throughout the pandemic is that the maritime provinces that received COVID zero the approach has had little pre-existing immunity in the last two years.
But when Omicron struck in December, it took advantage of the province’s lack of population immunity.
“It was like a bang, here it is,” he said. “And it is still going through the population and yet we had stricter measures than Ontario and other provinces, but they went through all those different waves that we did not have.”
How do we get to the “COVID era” with constantly evolving variants?
Although it is unclear whether newly discovered levels of population immunity in Canada and consistently high vaccination rates will prevent future waves of the virus and bring us closer to seasonality, there are early indications from other countries that we may be able to better predict the waves in the future.
Tom Wenseleers, an evolutionary biologist at KU Leuven University in Belgium, said: Twitter that South Africa is beginning to show signs of seasonality with COVID, which could look like “a major wave every six months with significant mortality and morbidity”.
BA.4 & BA.5 The increase in new confirmed Covid cases in South Africa due to the Omicron sub-variable gives a good idea of what the endemic balance will be like: a significant wave every 6 months with significant mortality & morbidity. 🧵 pic.twitter.com/I9jd5gMIPG
– @ TWenseleers
“The impact on the healthcare system of both BA.2.12.1 and BA.4 and BA.5 is not really clear yet. They will cause waves of infections, for sure, but the impact on hospitalizations and expected mortality can not yet. “to be appreciated right now,” he told CBC News.
“Early data seem to suggest similar seriousness to the original Omicron in terms of hospitalization ratio … but it is too early to conclude.”
De Oliveira, who led the research team that identified subtypes of BA.4 and BA.5 in South Africa, said declining immunity to infection and vaccination could affect their spread.
“The only thing that can play a role in this is just the timing of BA.1, so we look at the data very carefully,” he said.
“We are talking about three or four months after the peak of BA.1 and we know that it is about three or four months when the population’s immunity begins to decline.”
A new preprint study A co-author of de Oliveira, which has not yet been peer-reviewed, suggested that there could be “growth advantages” for BA.4 and BA.5 over BA.2 in South Africa that could potentially trigger a another wave, but whether this will happen there or in other countries remains to be seen.
And more variations are possible on the horizon.
“This seems to be the behavior of SARS-CoV-2 and I think we should not be shocked to see another variant,” said Alyson Kelvin, a virologist at the Canadian Center for Vaccines and the Vaccine and Infectious Diseases Agency. in Saskatoon.
“But keep planning for them, unfortunately, which I think affects our vaccination strategies… until you start [an updated vaccine] there is a new variation outside “.
People endure the snow to line up for the COVID-19 test in early January in Vancouver. The chaotic COVID wave pattern in Canada has not yet shown significant signs of seasonal transmission, but there are some indications that we could eventually get there. (Ben Nelms / CBC)
Although the chaotic pattern of COVID waves in Canada has not yet shown significant signs of seasonality, there are some indications that we are moving towards it.
“There is still seasonality associated with COVID. This does not mean it fits in perfectly, but of course there are times during the colder months in Canada where we see more cases,” said Dr. Isaac Bogoch, infectious disease physician at Toronto General Hospital.
“Hopefully this wave will subside and we have a great summer ahead of us … but can this be disrupted by a very contagious variant? Maybe. Maybe.”
Gardam said that if we look at other viruses in the long run such as …
