Why restricting AstraZeneca vaccines in Canada means balancing 'vaccine risk vs. disease risk' - CBC.ca | Canada News Media
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Why restricting AstraZeneca vaccines in Canada means balancing 'vaccine risk vs. disease risk' – CBC.ca

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This is an excerpt from Second Opinion, a weekly roundup of health and medical science news emailed to subscribers every Saturday morning. If you haven’t subscribed yet, you can do that by clicking here.


Canada’s decision to suspend the use of the AstraZeneca-Oxford vaccine in Canadians under 55 during a surging third wave and a slow vaccination rollout is a calculated risk.

The National Advisory Committee on Immunization (NACI) updated its guidance to provinces and territories against the use of the vaccine for younger Canadians on Monday, following reports of rare but potentially fatal blood clots in Europe connected to the shot.

Health Canada says the benefits of the vaccine to protect against COVID-19 still outweigh the potential risks, with more than 300,000 doses of the shot administered and no cases of the serious clotting condition, known as vaccine-induced prothrombotic immune thrombocytopenia (VIPIT), in Canada. 

But the decision to restrict the use of one of four approved vaccines at a time when COVID-19 levels are rising again in Canada’s hardest hit provinces is a tough pill to swallow for some.

“It can be a very powerful tool when we’re at this stage of the pandemic where we’re talking about, in hotspots at least, the system getting to a point of potential collapse,” said Dr. Susy Hota, an infectious disease specialist at the University Health Network and an associate professor of medicine at the University of Toronto. 

“There are humans behind that story, and when you’re in a hospital where you’re seeing an exponential rise in the number of COVID-positive patients coming in, and your staff to help manage these patients is the same pool of staff — then those numbers aren’t adding up.”

But on an individual level, experts say the lack of data on the risk of VIPIT to Canadians from the AstraZeneca vaccine is concerning and NACI was right to err on the side of caution in order to avoid putting lives unnecessarily at risk. 

Pharmacist Abraam Rafael administers a COVID-19 vaccine to Maureen Doyle at his pharmacy in Toronto on March 14 as Ontario starts administering the AstraZeneca vaccine for COVID-19 to residents aged 60-64. (Cole Burston/The Canadian Press)

Race between vaccines and variants

Ontario has more ICU admissions than at any other point in the pandemic, B.C. has had its highest single-day number of new cases to date, and Quebec saw its biggest one-day spike in almost two months as more transmissible variants are spreading rapidly across Canada.

The good news is that vaccines work; eight provinces and territories reported no new deaths in a single day this week, and the decision to prioritize COVID-19 vaccines in long-term care has led to a dramatic drop in deaths in residents. 

The bad news is that the race between vaccines and variants is taking on new urgency; the majority of vulnerable Canadians are still unvaccinated and the third wave is hitting younger adults harder and showing no signs of slowing down. 

“It’s so complicated, because I look at it as being two things: What is the absolute risk of this potentially related severe side effect versus the absolute risk of the disease?” said Dr. Lynora Saxinger, an infectious diseases physician and an associate professor at the University of Alberta faculty of medicine in Edmonton.

“The other consideration is, what is the public backlash to potential outcomes of any particular course of action?”

WATCH | AstraZeneca now only recommended for Canadians over 55:

Canada’s vaccine advisory committee has changed its advice and now says the AstraZeneca COVID-19 vaccine should only be given to people aged 55 and up following concerns it could be linked to a rare blood clot. 2:21

Health Canada says VIPIT occurs at a rate of about one in 100,000 people vaccinated, with a mortality rate of about 40 per cent, although more research is needed and that risk is reduced if treated early enough. The total number of people in Europe who got the rare blood clots after vaccination is small — as of Thursday, dozens of cases have been reported compared to millions who received the shot.

But crucially, the people who appear to have an elevated risk of the rare blood clots are not the same age group most at risk from COVID-19.

“If you look at the average 30 or 40-year-old Canadian, their risk of getting severely ill from COVID based on our current experience is substantially less,” said Dr. Andrew Morris, a professor of infectious diseases at the University of Toronto.

“You’re asking them for the good of the country to take on a risk that they wouldn’t even get with COVID. So why would you give them a vaccine that is more likely to give them harm then COVID is? It makes no sense.”

Canada has had close to 23,000 COVID-19 deaths in the year since the pandemic began, but fewer than a thousand of those have been in people under 60 and just over 300 in Canadians under 50.

“What happens to NACI if they say that everything is fine, despite the European experience which really brings it into question, and then we have even one death in Canada from this?” said Morris. “NACI would be just absolutely raked over the coals.”

‘Vaccine risk versus disease risk’

Dr. David Fisman, an epidemiologist at the University of Toronto’s Dalla Lana School of Public Health, said the debate over whether suspending the vaccine in younger Canadians was the right decision is due to a miscalculation of risks for that age group.

“I think what you see is a bit of wire crossing around vaccine risk versus disease risk,” he said.

There is also a risk of clots from getting COVID-19, but that’s conditional on getting the disease first, and there are other vaccines to protect against it, he said, rather than using a vaccine linked to adverse events in this age group.

“The adverse effect here is rather devastating,” he said. “[VIPIT] seems to be killing about half the people who suffer these consequences, and is highly likely to cause permanent neurological damage in survivors.”

“Given that these are young people working in healthcare, it is likely that vaccination is conferring damage or death that they would not have suffered otherwise.”

Dr. Menaka Pai, a clinical hematologist at McMaster University and a member of Ontario’s COVID-19 Science Advisory Table, says the risks associated with VIPIT in younger adults are dangerous enough to warrant halting its use in those under 55.

“The clots that we see with VIPIT — they’re serious. If you’re not aware of them they can be hard to diagnose, they can be hard to treat,” she said. 

“If you’re older and likely to experience all the other horrible things that COVID does, including killing you, then your decision about urgency and needing any vaccine frankly is really different from somebody who is younger and probably better able to weather the storms of COVID.” 

WATCH | Should people who’ve had the AstraZeneca vaccine be concerned?

Infectious disease experts take questions about the changing advice for the AstraZeneca COVID-19 vaccine including if those who’ve had a shot should be concerned. 4:22

Pai says critics of NACI’s decision are inaccurately drawing comparisons with the risk of VIPIT to the risk of birth control pills, which also carry an increased risk of blood clots.

“The reality is that every year a little under one in 3,000 women will get a blood clot on the combined oral contraceptive pill and every year one in 300 pregnant women will get a blood clot,” she said. 

“But the clots that you get on those hormones are very different from the clots that we’re seeing related to the AstraZeneca vaccine.” 

Raywat Deonandan, an epidemiologist and associate professor at the University of Ottawa, says if the risk from the AstraZeneca-Oxford vaccine to younger Canadians can be mitigated with another COVID-19 shot, then the decision to halt the use of it makes sense.

“This is not the same as going to a place like Brazil where the disease is rampaging out of control,” he said. 

“Whereas this is the only vaccine you have available to you — take it now or I can’t guarantee you will be alive in a month. It’s a different scenario entirely.” 

But Deonandan says he can sympathize with critics of NACI’s recommendations to suspend the vaccine because of the damage the decision may do to the public perception of COVID-19 vaccine safety overall. 

“If you are saving any lives, you’re saving one or two lives [from VIPIT],” he said.  “On the other hand, you’re creating such distrust of the vaccine you may be causing hundreds, possibly thousands of deaths from people not taking the vaccine.” 

“But given what NACI’s job is, which is to advise how best to deploy vaccines, they used the best evidence and came upon the right decision for their mandate.” 


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STD epidemic slows as new syphilis and gonorrhea cases fall in US

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NEW YORK (AP) — The U.S. syphilis epidemic slowed dramatically last year, gonorrhea cases fell and chlamydia cases remained below prepandemic levels, according to federal data released Tuesday.

The numbers represented some good news about sexually transmitted diseases, which experienced some alarming increases in past years due to declining condom use, inadequate sex education, and reduced testing and treatment when the COVID-19 pandemic hit.

Last year, cases of the most infectious stages of syphilis fell 10% from the year before — the first substantial decline in more than two decades. Gonorrhea cases dropped 7%, marking a second straight year of decline and bringing the number below what it was in 2019.

“I’m encouraged, and it’s been a long time since I felt that way” about the nation’s epidemic of sexually transmitted infections, said the CDC’s Dr. Jonathan Mermin. “Something is working.”

More than 2.4 million cases of syphilis, gonorrhea and chlamydia were diagnosed and reported last year — 1.6 million cases of chlamydia, 600,000 of gonorrhea, and more than 209,000 of syphilis.

Syphilis is a particular concern. For centuries, it was a common but feared infection that could deform the body and end in death. New cases plummeted in the U.S. starting in the 1940s when infection-fighting antibiotics became widely available, and they trended down for a half century after that. By 2002, however, cases began rising again, with men who have sex with other men being disproportionately affected.

The new report found cases of syphilis in their early, most infectious stages dropped 13% among gay and bisexual men. It was the first such drop since the agency began reporting data for that group in the mid-2000s.

However, there was a 12% increase in the rate of cases of unknown- or later-stage syphilis — a reflection of people infected years ago.

Cases of syphilis in newborns, passed on from infected mothers, also rose. There were nearly 4,000 cases, including 279 stillbirths and infant deaths.

“This means pregnant women are not being tested often enough,” said Dr. Jeffrey Klausner, a professor of medicine at the University of Southern California.

What caused some of the STD trends to improve? Several experts say one contributor is the growing use of an antibiotic as a “morning-after pill.” Studies have shown that taking doxycycline within 72 hours of unprotected sex cuts the risk of developing syphilis, gonorrhea and chlamydia.

In June, the CDC started recommending doxycycline as a morning-after pill, specifically for gay and bisexual men and transgender women who recently had an STD diagnosis. But health departments and organizations in some cities had been giving the pills to people for a couple years.

Some experts believe that the 2022 mpox outbreak — which mainly hit gay and bisexual men — may have had a lingering effect on sexual behavior in 2023, or at least on people’s willingness to get tested when strange sores appeared.

Another factor may have been an increase in the number of health workers testing people for infections, doing contact tracing and connecting people to treatment. Congress gave $1.2 billion to expand the workforce over five years, including $600 million to states, cities and territories that get STD prevention funding from CDC.

Last year had the “most activity with that funding throughout the U.S.,” said David Harvey, executive director of the National Coalition of STD Directors.

However, Congress ended the funds early as a part of last year’s debt ceiling deal, cutting off $400 million. Some people already have lost their jobs, said a spokeswoman for Harvey’s organization.

Still, Harvey said he had reasons for optimism, including the growing use of doxycycline and a push for at-home STD test kits.

Also, there are reasons to think the next presidential administration could get behind STD prevention. In 2019, then-President Donald Trump announced a campaign to “eliminate” the U.S. HIV epidemic by 2030. (Federal health officials later clarified that the actual goal was a huge reduction in new infections — fewer than 3,000 a year.)

There were nearly 32,000 new HIV infections in 2022, the CDC estimates. But a boost in public health funding for HIV could also also help bring down other sexually transmitted infections, experts said.

“When the government puts in resources, puts in money, we see declines in STDs,” Klausner said.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

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World’s largest active volcano Mauna Loa showed telltale warning signs before erupting in 2022

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WASHINGTON (AP) — Scientists can’t know precisely when a volcano is about to erupt, but they can sometimes pick up telltale signs.

That happened two years ago with the world’s largest active volcano. About two months before Mauna Loa spewed rivers of glowing orange molten lava, geologists detected small earthquakes nearby and other signs, and they warned residents on Hawaii‘s Big Island.

Now a study of the volcano’s lava confirms their timeline for when the molten rock below was on the move.

“Volcanoes are tricky because we don’t get to watch directly what’s happening inside – we have to look for other signs,” said Erik Klemetti Gonzalez, a volcano expert at Denison University, who was not involved in the study.

Upswelling ground and increased earthquake activity near the volcano resulted from magma rising from lower levels of Earth’s crust to fill chambers beneath the volcano, said Kendra Lynn, a research geologist at the Hawaiian Volcano Observatory and co-author of a new study in Nature Communications.

When pressure was high enough, the magma broke through brittle surface rock and became lava – and the eruption began in late November 2022. Later, researchers collected samples of volcanic rock for analysis.

The chemical makeup of certain crystals within the lava indicated that around 70 days before the eruption, large quantities of molten rock had moved from around 1.9 miles (3 kilometers) to 3 miles (5 kilometers) under the summit to a mile (2 kilometers) or less beneath, the study found. This matched the timeline the geologists had observed with other signs.

The last time Mauna Loa erupted was in 1984. Most of the U.S. volcanoes that scientists consider to be active are found in Hawaii, Alaska and the West Coast.

Worldwide, around 585 volcanoes are considered active.

Scientists can’t predict eruptions, but they can make a “forecast,” said Ben Andrews, who heads the global volcano program at the Smithsonian Institution and who was not involved in the study.

Andrews compared volcano forecasts to weather forecasts – informed “probabilities” that an event will occur. And better data about the past behavior of specific volcanos can help researchers finetune forecasts of future activity, experts say.

(asterisk)We can look for similar patterns in the future and expect that there’s a higher probability of conditions for an eruption happening,” said Klemetti Gonzalez.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

The Canadian Press. All rights reserved.

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Waymo’s robotaxis now open to anyone who wants a driverless ride in Los Angeles

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Waymo on Tuesday opened its robotaxi service to anyone who wants a ride around Los Angeles, marking another milestone in the evolution of self-driving car technology since the company began as a secret project at Google 15 years ago.

The expansion comes eight months after Waymo began offering rides in Los Angeles to a limited group of passengers chosen from a waiting list that had ballooned to more than 300,000 people. Now, anyone with the Waymo One smartphone app will be able to request a ride around an 80-square-mile (129-square-kilometer) territory spanning the second largest U.S. city.

After Waymo received approval from California regulators to charge for rides 15 months ago, the company initially chose to launch its operations in San Francisco before offering a limited service in Los Angeles.

Before deciding to compete against conventional ride-hailing pioneers Uber and Lyft in California, Waymo unleashed its robotaxis in Phoenix in 2020 and has been steadily extending the reach of its service in that Arizona city ever since.

Driverless rides are proving to be more than just a novelty. Waymo says it now transports more than 50,000 weekly passengers in its robotaxis, a volume of business numbers that helped the company recently raise $5.6 billion from its corporate parent Alphabet and a list of other investors that included venture capital firm Andreesen Horowitz and financial management firm T. Rowe Price.

“Our service has matured quickly and our riders are embracing the many benefits of fully autonomous driving,” Waymo co-CEO Tekedra Mawakana said in a blog post.

Despite its inroads, Waymo is still believed to be losing money. Although Alphabet doesn’t disclose Waymo’s financial results, the robotaxi is a major part of an “Other Bets” division that had suffered an operating loss of $3.3 billion through the first nine months of this year, down from a setback of $4.2 billion at the same time last year.

But Waymo has come a long way since Google began working on self-driving cars in 2009 as part of project “Chauffeur.” Since its 2016 spinoff from Google, Waymo has established itself as the clear leader in a robotaxi industry that’s getting more congested.

Electric auto pioneer Tesla is aiming to launch a rival “Cybercab” service by 2026, although its CEO Elon Musk said he hopes the company can get the required regulatory clearances to operate in Texas and California by next year.

Tesla’s projected timeline for competing against Waymo has been met with skepticism because Musk has made unfulfilled promises about the company’s self-driving car technology for nearly a decade.

Meanwhile, Waymo’s robotaxis have driven more than 20 million fully autonomous miles and provided more than 2 million rides to passengers without encountering a serious accident that resulted in its operations being sidelined.

That safety record is a stark contrast to one of its early rivals, Cruise, a robotaxi service owned by General Motors. Cruise’s California license was suspended last year after one of its driverless cars in San Francisco dragged a jaywalking pedestrian who had been struck by a different car driven by a human.

Cruise is now trying to rebound by joining forces with Uber to make some of its services available next year in U.S. cities that still haven’t been announced. But Waymo also has forged a similar alliance with Uber to dispatch its robotaxi in Atlanta and Austin, Texas next year.

Another robotaxi service, Amazon’s Zoox, is hoping to begin offering driverless rides to the general public in Las Vegas at some point next year before also launching in San Francisco.

The Canadian Press. All rights reserved.

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