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Canada We probably won't reach herd immunity against COVID-19 any time soon, but it's OK, experts say

12:51  05 may  2021
12:51  05 may  2021 Source:   cbc.ca

COVID protocol-related absences: 04/25

  COVID protocol-related absences: 04/25 Each day, the NHL will publicly release the list of players that are unavailable to their respective teams due to being in COVID-19 Protocol. Here is today’s list: Calgary – Josh Leivo Colorado – Joonas Donskoi, Mikko Rantanen New Jersey – P.K.Calgary – Josh Leivo

Medical experts told The New York Times that the US must work to limit the rates of severe infections leading to hospitalisations and deaths as pandemic-related restrictions are relaxed despite the imbalance of vaccinated and unvaccinated Americans. The goal over “a generation or two” would be to transition the coronavirus into a cold-like virus that is easier to control, experts told the newspaper. “ We cannot eradicate COVID ,” one professor said . “ We want COVID to become like any other disease or respiratory virus that we can deal with on a yearly basis.”

Why won ’ t we reach herd immunity ? Herd immunity rates change based on how contagious a given virus is, the efficacy of available vaccines, the number of people who receive the vaccine, and the propensity of the virus to evolve, among other factors. Measles is a good example. Unlike measles, scientists are uncertain how long Covid immunity lasts, though for natural immunity it could be as short as a few months. Many experts believe people will need either boosters or variant-specific vaccines in the future. Even before more contagious “escape variants” were identified, such as the

a close up of a circuit board: Empty vials of the AstraZeneca-Oxford COVID-19 vaccine given to customers are lined up at a Toronto pharmacy last month. Experts say that even as more Canadians are getting vaccinated, reaching herd immunity isn't inevitable, with several barriers in the way. © Nathan Denette/The Canadian Press Empty vials of the AstraZeneca-Oxford COVID-19 vaccine given to customers are lined up at a Toronto pharmacy last month. Experts say that even as more Canadians are getting vaccinated, reaching herd immunity isn't inevitable, with several barriers in the way.

Every day, more and more Canadians are vaccinated against COVID-19.

It has often been suggested that as this trend continues, we will soon reach a point where so many people are invulnerable to the virus that it will largely die out due to a lack of hosts to infect — offering indirect protection to the entire population, even those who are not immunized.

COVID protocol-related absences: 04/27/21

  COVID protocol-related absences: 04/27/21 Each day, the NHL will publicly release the list of players that are unavailable to their respective teams due to being in COVID-19 Protocol. Here is today’s list: Anaheim – Adam Henrique Calgary – Josh Leivo Montreal – TBA New Jersey – P.K.Anaheim – Adam Henrique

Some experts and healthcare officials believe that herd immunity cannot be reached in the immediate future or is simply impossible, with the deadly virus here to stay for years, but with less intensity, The New York Times reported on Monday. While it is hard to predict future death rates and how much Experts assume that vaccination along with vigilant testing and tracking are still crucial for controlling the disease and transforming it to a seasonal cold that would impact only the young and healthy. In the long run, it ' s thought that COVID - 19 will become a common flu as people will overcome the virus at

US probably won ’ t reach Covid herd immunity , experts conclude. When will the United States reach herd immunity to COVID - 19 ? Experts now say it might not — but that doesn't mean the virus has to POPULAR. Health Experts Warn U . S . Not Likely to Hit Herd Immunity Any Time Soon .

The goal of "herd immunity" is often described as just around the corner, signalling a return to pre-pandemic normality.

But will we actually get there?

Probably not, say epidemiologists and mathematicians who have been studying the latest numbers closely. At least, not any time soon.

These experts highlight several major barriers that stand in the way: the arrival of new COVID-19 variants, vaccine hesitancy among adults and the fact that millions of children can't be vaccinated at all. Even in a best-case scenario, this makes the herd-immunity threshold a high bar. Practically speaking, it could be out of reach.

a group of people in a room: Workers are vaccinated at a clinic in Montreal. The exact percentage of the population that needs to be fully vaccinated or recovered from COVID-19 in order to reach herd immunity is uncertain and can change. Recent estimates put the threshold as high as 80 or close to 90 per cent. © Paul Chiasson/The Canadian Press Workers are vaccinated at a clinic in Montreal. The exact percentage of the population that needs to be fully vaccinated or recovered from COVID-19 in order to reach herd immunity is uncertain and can change. Recent estimates put the threshold as high as 80 or close to 90 per cent.

But that's no reason to despair. It's not herd immunity or bust.

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Experts now say that herd immunity is not likely in the US . Instead, they expect COVID will become a manageable virus that will circulate throughout the population for years to come. But the way this article breaks it down is something I recognize. COVID will join the ranks of influenza and pneumonia. I still get nervous when I hear someone has pneumonia, but it ’ s no longer an automatic death sentence. As I mentioned once, I had influenza and whereas I didn’ t actually think I would die, I saw how people could.

Scientists and public health experts instead believe that the virus will continue to circulate on a more manageable level. The continuation of immunizations is still crucial to getting severe infections under control. The virus is unlikely to go away. But we want to do all we can to check that it ’ s likely to become a As daily vaccination rates decline, experts now predict the United States will not reach a point where enough Americans are protected from the virus to eliminate the pathogen. New variants are spreading too quickly and the vaccinations are proceeding too slowly for herd immunity to be reached anytime soon

Unlike politicians, epidemiologists don't obsess over a precise number, which can be hard to pin down. In practice, they say, the closer we get to that threshold — whatever it actually is — the better. And as more people are immunized, life can begin returning to something that feels much more normal.

Why herd immunity is such a high bar

Ashleigh Tuite, an epidemiologist and mathematical modeller with the University of Toronto's Dalla Lana School of Public Health, has run the calculations over and over — and to her, the results look pretty clear.

"I think it's likely that we won't achieve herd immunity," she said. "But I don't think that's a bad thing."

The reason it looks out of reach, to Tuite, has to do with cold, hard math.

The herd-immunity threshold is calculated using an equation with two main variables: the transmissibility of a virus and the effectiveness of our immune response — which, at a population level, comes from a combination of vaccination and natural infection.

COVID protocol-related absences: 05/13/21

  COVID protocol-related absences: 05/13/21 Each day, the NHL will publicly release the list of players that are unavailable to their respective teams due to being in COVID-19 Protocol. Here is today’s list: © Isaiah J. Downing-USA TODAY Sports Colorado – Devan DubnykSt. Louis – Jake WalmanWashington – Evgeny KuznetsovAs a reminder, inclusion on this list does not mean that a player has tested positive for Coronavirus or even that they have been confirmed as a close contact to another positive person.

Experts now say it might not — but that doesn' t mean the virus has to remain a "society disrupter." That' s according to a new report in The New York Times , which says there is now a "widespread consensus among scientists and public health experts " that in the U . S ., the " herd immunity threshold is not John Oliver laid into Fox News host Tucker Carlson Sunday on Last Week Tonight With John Oliver, for continuing to plant seeds of doubt in the minds of his viewers concerning the COVID - 19 vaccines. Despite the vaccines being shown to be safe and incredibly effective in the fight against

Hard as it may be to hear, he said , he believes that it may take close to 90 percent immunity to bring the virus to a halt — almost as much as is needed to stop a measles outbreak. Asked about Dr. Fauci’ s conclusions, prominent epidemiologists said that he might be proven right. It also became clearer later that “superspreader events,” in which one person infects dozens or even hundreds of others, played a large role in spreading Covid - 19 . Such events, in “normal” populations — in which no one wears masks and everyone attends events like parties, basketball tournaments or Broadway shows — can

The exact percentage of the population that needs to be fully vaccinated or recovered from COVID-19 in order to reach herd immunity is uncertain and can change. Earlier in the pandemic, the threshold was estimated at about 70 per cent. But more recent estimates range as high as 80 or even close to 90 per cent.

One of the biggest reasons for the increase is that new variants are estimated to be 50 to 60 per cent more transmissible than the original "wild type" strain of the virus. That alone significantly raises the herd-immunity threshold from what it used to be.

Further complicating matters is the fact that neither vaccination nor natural infection confers perfect immunity.

Questions remain about the potential for a vaccinated person to carry small amounts of the virus without having any symptoms but still being able to transmit the virus to non-immunized people.

Similarly, questions remain about how long immunity from natural infection will last and how it will stand up to new variants.

Millions of kids left out of vaccinations

Another big challenge is the fact that vaccines are only approved for Canadians aged 16 and up.

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Health Canada is in the process of reviewing an application from Pfizer-BioNTech for use of its vaccine in children as young as 12. That approval could come soon, but even if it does, it will still leave 4.8 million kids — or 13 per cent of the population — ineligible for any vaccine.

a group of people wearing costumes and standing in front of a crowd: The Pfizer-BioNTech vaccine may soon be approved for kids as young as 12 in Canada, but that would still leave 4.8 million children ineligible for any type of vaccination against COVID-19. © Evan Mitsui/CBC The Pfizer-BioNTech vaccine may soon be approved for kids as young as 12 in Canada, but that would still leave 4.8 million children ineligible for any type of vaccination against COVID-19.

Video: Why it’s difficult to pinpoint when herd immunity will be reached (cbc.ca)

That throws a huge wrench in any plans to reach herd immunity, says Caroline Colijn, a mathematics professor at Simon Fraser University in Vancouver and the Canada 150 Research Chair in Mathematics for Evolution, Infection and Public Health.

"We need to be vaccinating kids as soon as we can," she said.

Recent modelling Colijn conducted shows an enormous reduction in viral spread in a scenario where kids as young as 10 can be vaccinated.

In fact, if 70 per cent of those aged 10 to 19 were fully vaccinated, along with a higher proportion of adults, her modelling suggests we could get close to herd immunity.

"Whether you're exactly bang on that threshold or not is not the interesting point. The point is that vaccinating that age group is really, really important," Colijn said.

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She cautions, however, that this modelling rests on several "optimistic" assumptions.

The scenarios Colijn examined assume that natural immunity protects completely against reinfection and does not wane, that new variants will not reduce the effectiveness of vaccines and that significant proportions of the adult population will choose to get vaccinated.

Vaccine hesitancy among adults

Without the ability to vaccinate children, close to 100 per cent of the adult population would need to be vaccinated in order to reach herd immunity, says Raywat Deonandan, an epidemiologist at the University of Ottawa.

That's impossible, he says, given the significant proportion of Canadians who are vaccine-hesitant.

a person posing for the camera: University of Ottawa epidemiologist Raywat Deonandan says Canada can achieve the same benefits of herd immunity by maintaining some degree of public health measures along with growing levels of vaccination. © Evan Mitsui/CBC University of Ottawa epidemiologist Raywat Deonandan says Canada can achieve the same benefits of herd immunity by maintaining some degree of public health measures along with growing levels of vaccination.

"Vaccine hesitancy is a barrier," Deonandan said. "It's not insurmountable, but it is going to be a barrier."

Recent polling has shown that Canadians have warmed to vaccines, with a growing proportion saying they'll get vaccinated as soon as they have the chance. But about 10 to 15 per cent have consistently said they will not accept a vaccine at all.

On top of that, there are people on the fence. It's the behaviour of this in-between group that may ultimately determine how close we get to herd immunity — which is why a variety of efforts are underway to encourage Canadians to get their shots.

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In the United States, vaccine hesitancy is increasingly seen as a major and perhaps permanent barrier to herd immunity. The vaccine rollout south of the border got off to a fast start but has been slowing as time goes on and the supply of doses starts to outpace demand.

Forecasting the near future

What does the future hold for Canada? That's something Paul Minshull studies closely.

Minshull is the founder of Scarsin Corporation, an enterprise forecasting firm based in Markham, Ont., that has turned its detailed modelling software to the task of predicting where COVID-19 will go next.

Scarsin's models are constantly updated with the latest data and combined with realistic assumptions about the things we don't know for sure — such as the true effectiveness of vaccines against transmission and the actual level of vaccine hesitancy we'll see among Canadians.

a man standing in front of a computer: Paul Minshull is founder of Scarsin Corporation, an enterprise forecasting firm in Ontario that has turned its detailed modelling software to the task of predicting where COVID-19 will go next. © Evan Mitsui/CBC Paul Minshull is founder of Scarsin Corporation, an enterprise forecasting firm in Ontario that has turned its detailed modelling software to the task of predicting where COVID-19 will go next.

The modelling boils everything down into a simple bottom line: the number of Canadians who are expected to be genuinely protected from COVID-19 through effective vaccination or natural infection.

Come October — when everyone who is eligible for vaccination is expected to have had a full complement of doses made available to them — Scarsin's latest modelling forecasts 25.2 million Canadians will be vaccinated, almost all of them with full doses. That's 66 per cent of the population.

But the model also makes some downward adjustments to account for the fact that vaccines aren't perfect and that vaccinated individuals might asymptomatically transmit the virus. It also makes some upward adjustments by adding in an estimate for people who are unvaccinated but have "recovered immunity" due to natural infection.

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Add it all up and, according to Minshull, "the likely scenario for Canada ... is that between 58 per cent and 64 per cent of the population will have immunity this year — well short of what is needed for herd immunity."

These results may sound disappointing, but Scarsin's modelling also predicts what effect this level of immunity will have on the severity of COVID-19. And on that front, the future looks a lot brighter.

"The good news is that things are going to improve significantly over the summer and into the fall as more and more Canadians get vaccinated," Minshull wrote in a recent analysis.

Less of a finish line, more of a seesaw

That's the kind of future Erin Strumpf envisions for late 2021, as well.

Strumpf, an associate professor in the department of economics and the department of epidemiology, biostatistics and occupational Health at McGill University in Montreal, said she believes the end of the pandemic looks more like a drawn-out affair, rather than a hard stop.

"We're going to have to live with potentially fewer people in stores and retail spaces," she said. "We're going to keep wearing masks. We're going to still continue to work from home and maybe some in the office. So it'll be more of a gradual adjustment."

a woman wearing glasses and smiling at the camera: Erin Strumpf, a health economics expert at McGill University in Montreal, says she believes the end of the pandemic looks more like a drawn-out affair, rather than a hard stop. © CBC Erin Strumpf, a health economics expert at McGill University in Montreal, says she believes the end of the pandemic looks more like a drawn-out affair, rather than a hard stop.

Herd immunity, Strumpf said, has often been likened to a finish line: Once we cross it, the race is over.

In reality, she said, the next stage in the struggle against COVID-19 is more like a seesaw: The virus will flare up at different times and in different places, and we will have to respond accordingly in order to knock it back down. But overall, it won't be nearly as severe as it's been over the past 14 months.

Deonandan, with the University of Ottawa, says we can achieve the same benefits of herd immunity by maintaining some degree of public health measures along with growing levels of vaccination.

"If we're willing to have mitigation tools in place for a long time, we can achieve effective herd immunity," Deonandan said. "It's just not what people think about when they think about herd immunity. They think about a free-for-all."

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usr: 0
This is interesting!