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Study offers 'promising' evidence that at least 1 COVID-19 vaccine may curb virus transmission – CBC.ca

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Real-world findings are starting to back expectations for the level of protection provided by several leading coronavirus vaccines, but there’s still a burning question among scientists: Could the shots actually reduce virus transmission as well?

New research out of Israel offers early clues that at least one vaccine — the mRNA-based option from Pfizer-BioNTech, which is also being used here in Canada — may lead to lower viral loads, suggesting it might be harder for someone to spread the virus if they get infected post-vaccination.

In a study released publicly on Monday as an unpublished, non-peer-reviewed preprint, a team of researchers from the Israel Institute of Technology, Tel Aviv University and Maccabi Healthcare Services found the viral load was reduced four-fold for infections that occur 12 to 28 days after a first dose of the vaccine.

“These reduced viral loads hint to lower infectiousness, further contributing to vaccine impact on virus spread,” the researchers wrote.

Virologist Jason Kindrachuk, an assistant professor in the department of medical microbiology at the University of Manitoba, said it’s been a waiting game to figure out whether the protection from illness offered by mRNA vaccines might also curb transmission — a key tool for winding down the pandemic.

“So the data from this, I think, is important,” he said. “It doesn’t answer all the questions, but it starts to tell us that there actually might be some added benefit to these vaccines beyond just reducing severe disease.”

Toronto-based infectious disease specialist Dr. Isaac Bogoch, a member of Ontario’s vaccine task force, agreed these early findings — which still require peer-review — aren’t a scientific “home run,” but do offer hope in the fight against COVID-19.

“This would point in the direction that people who have been vaccinated, who are still infected, may be less likely to transmit starting at about 12 days after their vaccine,” he said.

‘Significantly reduced’ viral loads

Israel is among the world leaders for COVID-19 vaccination rates, with Maccabi Healthcare Services vaccinating more than 650,000 people by Jan. 25, the paper noted, giving the researchers a large pool of data compared to what exists so far in many other countries. 

The team analyzed COVID-19 test results from roughly 2,900 people between the ages of 16 and 89, comparing the cycle threshold values of post-vaccination infections after a first dose with those of positive tests from unvaccinated patients.

So, what are cycle threshold values, and how does that potentially tie to viral loads and virus transmission?

Standard polymerase chain reaction (PCR) tests for COVID-19 identify the viral infection by amplifying the virus’s RNA until it hits a level where it can be detected by the test. Multiple rounds of amplification may be required — and the cycle threshold value refers to the number of rounds needed to spot the virus.

Toronto-based infectious disease specialist Dr. Isaac Bogoch, a member of Ontario’s vaccine task force, agrees these early findings — which still require peer-review — offer some hope in the fight against COVID-19. (Maggie MacPherson/CBC)

“If you can detect the virus with very few cycles, there’s probably a lot of virus there,” Bogoch explained. “If you need to keep looking and looking and looking and looking for it, it might be there — it’s just a lot harder to find evidence of the virus genetic material.”

A higher cycle threshold, then, usually means there’s less virus genetic material present, which usually translates to people being less contagious, he said.

Based on an analysis comparing post-vaccination test results up to Day 11 to the unvaccinated control group, the Israeli researchers found “no significant difference” in the distribution of cycle threshold values for several viral genes.

That changed by 12 days after vaccination, with the team finding a “significant” increase in cycle thresholds up to 28 days later.

A team of researchers from the Israel Institute of Technology, Tel Aviv University and Maccabi Healthcare Services found the viral load was reduced four-fold for infections happening 12 to 28 days after a first dose of the Pfizer-BioNTech mRNA vaccine. The findings have yet to be peer-reviewed and published in a medical journal. (Evan Mitsui/CBC News)

The result suggests infections occurring 12 days or longer following just one vaccine dose have “significantly reduced viral loads, potentially affecting viral shedding and contagiousness as well as severity of the disease,” the team concluded.

It’s a finding that appears to mimic the efficacy of the Pfizer-BioNTech vaccine in its clinical trials, which offered some early protection starting 12 days after the first dose and fully kicks in a week after the second shot, with a reported efficacy of around 95 per cent.

More research needed, experts say

The observational study was not a randomized controlled trial — meaning researchers couldn’t conclude a direct cause-and-effect relationship — and has not yet been published in a scientific journal. The research also has notable limitations, its authors acknowledged. 

For one, the group of vaccinated individuals may differ in key ways from the demographically matched control group, such as their general health. The study also didn’t account for variants of the virus that may be associated with different viral loads, the team wrote.

Indeed, those variants are already proving to be roadblocks in the fight against COVID-19, with concerns ranging from higher transmissibility to reduced vaccine efficacy, including concern in South Africa and beyond after a small and yet-to-be-published study suggested the Oxford-AstraZeneca vaccine offered minimal protection against mild infection from the country’s now-dominant B1351 variant. 

With those concerns in mind, experts who spoke with CBC News about the Israeli study stressed that more research is needed to back up the results on a broader scale, and among diverse populations, before being used to fuel policy changes or current approaches to vaccination efforts.

“The data needs to be reviewed by experts and confirmed that it stands up to the quality that we would want to make a conclusion,” said vaccinologist Alyson Kelvin, an assistant professor at Dalhousie University in Halifax who works with Canadian vaccine developer VIDO-InterVac in Saskatoon.

WATCH | The impact of variants on the race to vaccinate: 

South Africa has halted its rollout of the AstraZeneca COVID-19 vaccine after a study showed it offered minimal protection against mild infection from a variant spreading there. While experts say it’s cause for concern, they say vaccines can be reconfigured to protect against mutations. 2:01

Even so, Kelvin said the data appeared to be treated with the necessary caution, and offers “promising evidence,” while Kindrachuk remains optimistic as well that the findings could prove a useful starting point.

“While we still have to have people using masks, and while we still have to have people distanced, the vaccines may actually also be able to reduce transmission,” he said. 

“So, those trends that we’re hoping to see, in regards to trying to curb community transmission for SARS-CoV-2, may be accelerated with a vaccine — and that will hopefully help us get out of this a little bit sooner.”


The Current21:46Vaccine concerns in South Africa

South Africa is facing another hurdle in its fight against COVID-19 after a new study suggested the Oxford-AstraZeneca vaccine is largely ineffective against the dominant variant spreading in that country. Dr. Rinesh Chetty, who works on the front lines of the pandemic in Durban, South Africa, weighs in on the findings. And Dr. Gerald Evans, an infectious disease specialist at Queen’s University and the Kingston Health Sciences Centre, tells us what it means for Canada’s vaccination efforts. 21:46

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Women in states with bans are getting abortions at similar rates as under Roe, report says

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Women living in states with abortion bans obtained the procedure in the second half of 2023 at about the same rate as before the U.S. Supreme Court overturned Roe v. Wade, according to a report released Tuesday.

Women did so by traveling out of state or by having prescription abortion pills mailed to them, according to the #WeCount report from the Society of Family Planning, which advocates for abortion access. They increasingly used telehealth, the report found, as medical providers in states with laws intended to protection them from prosecution in other states used online appointments to prescribe abortion pills.

“The abortion bans are not eliminating the need for abortion,” said Ushma Upadhyay, a University of California, San Francisco public health social scientist and a co-chair of the #WeCount survey. “People are jumping over these hurdles because they have to.”

Abortion patterns have shifted

The #WeCount report began surveying abortion providers across the country monthly just before Roe was overturned, creating a snapshot of abortion trends. In some states, a portion of the data is estimated. The effort makes data public with less than a six-month lag, giving a picture of trends far faster than the U.S. Centers for Disease Control and Prevention, whose most recent annual report covers abortion in 2021.

The report has chronicled quick shifts since the Supreme Court’s Dobbs v. Jackson Women’s Health Organization ruling that ended the national right to abortion and opened the door to enforcement of state bans.

The number of abortions in states with bans at all stages of pregnancy fell to near zero. It also plummeted in states where bans kick in around six weeks of pregnancy, which is before many women know they’re pregnant.

But the nationwide total has been about the same or above the level from before the ruling. The study estimates 99,000 abortions occurred each month in the first half of 2024, up from the 81,000 monthly from April through December 2022 and 88,000 in 2023.

One reason is telehealth, which got a boost when some Democratic-controlled states last year began implementing laws to protect prescribers. In April 2022, about 1 in 25 abortions were from pills prescribed via telehealth, the report found. In June 2024, it was 1 in 5.

The newest report is the first time #WeCount has broken down state-by-state numbers for abortion pill prescriptions. About half the telehealth abortion pill prescriptions now go to patients in states with abortion bans or restrictions on telehealth abortion prescriptions.

In the second half of last year, the pills were sent to about 2,800 women each month in Texas, more than 1,500 in Mississippi and nearly 800 in Missouri, for instance.

Travel is still the main means of access for women in states with bans

Data from another group, the Guttmacher Institute, shows that women in states with bans still rely mostly on travel to get abortions.

By combining results of the two surveys and comparing them with Guttmacher’s counts of in-person abortions from 2020, #WeCount found women in states with bans throughout pregnancy were getting abortions in similar numbers as they were in 2020. The numbers do not account for pills obtained from outside the medical system in the earlier period, when those prescriptions most often came from abroad. They also do not tally people who received pills but did not use them.

West Virginia women, for example, obtained nearly 220 abortions monthly in the second half of 2023, mostly by traveling — more than in 2020, when they received about 140 a month. For Louisiana residents, the monthly abortion numbers were about the same, with just under 700 from July through December 2023, mostly through shield laws, and 635 in 2020. However, Oklahoma residents obtained fewer abortions in 2023, with the monthly number falling to under 470 from about 690 in 2020.

Telehealth providers emerged quickly

One of the major providers of the telehealth pills is the Massachusetts Abortion Access Project. Cofounder Angel Foster said the group prescribed to about 500 patients a month, mostly in states with bans, from its September 2023 launch through last month.

The group charged $250 per person while allowing people to pay less if they couldn’t afford that. Starting this month, with the help of grant funding that pays operating costs, it’s trying a different approach: Setting the price at $5 but letting patients know they’d appreciate more for those who can pay it. Foster said the group is on track to provide 1,500 to 2,000 abortions monthly with the new model.

Foster called the Supreme Court’s 2020 decision “a human rights and social justice catastrophe” while also saying that “there’s an irony in what’s happened in the post-Dobbs landscape.”

“In some places abortion care is more accessible and affordable than it was,” she said.

There have no major legal challenges of shield laws so far, but abortion opponents have tried to get one of the main pills removed from the market. Earlier this year, the U.S. Supreme Court unanimously preserved access to the drug, mifepristone, while finding that a group of anti-abortion doctors and organizations did not have the legal right to challenge the 2000 federal approval of the drug.

This month, three states asked a judge for permission to file a lawsuit aimed at rolling back federal decisions that allowed easier access to the pill — including through telehealth.

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How many smoke-related deaths from wildfires are linked to climate change every year?

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Climate change may be contributing to thousands more wildfire smoke-related deaths every year than in previous decades, a new study suggests — results a Canadian co-author says underline the urgency of reducing planet-warming emissions.

The international study published Monday is one of the most rigorous yet in determining just how much climate change can be linked to wildfire smoke deaths around the world, said Sian Kou-Giesbrecht, an assistant professor at Dalhousie University.

“What stands out to me is that this proportion is increasing just so much. I think that it really kind of attests to just how much we need to take targeted action to reducing greenhouse-gas emissions,” she said in an interview.

The study estimates, using mathematical modeling, that about 12,566 annual wildfire smoke-related deaths in the 2010s were linked to climate change, up from about 669 in the 1960s, when far less carbon dioxide was concentrated in the atmosphere.

Translated to a proportion of wildfire smoke mortality overall, the study estimates about 13 per cent of estimated excessdeaths in the 2010s were linked to climate change, compared to about 1.2 per cent in the 1960s.

“Adapting to the critical health impacts of fires is required,” read the study, published in the peer-reviewed journal Nature Climate Change.

While wildfires are a natural part of the boreal forest ecosystem, a growing number of studies have documented how climate change, driven by the burning of fossil fuels, is making them larger and more intense — and contributing more to air pollution.

The same research group is behind another study published in the same journal Monday that suggests climate change increased the global area burned by wildfire by about 16 per cent from 2003 to 2019.

Those climate-fuelled fires then churn out more fine particle pollution, known as PM2.5, that’s tiny enough to get deep into the lungs — and in the long run can have serious health effects.

The study that estimated the scale of those effects is based on modeling, not historical data about reported deaths from air pollution.

Researchers used established public-health metrics for when pollution is thought to contribute to mortality, then figured out the extent to which wildfire smoke may have played a role in that overall exposure to arrive at the estimates.

Meanwhile, Health Canada estimates that between 2013 and 2018, up to 240 Canadians died every year due to short-term exposure to wildfire air pollution.

Kou-Giesbrecht said Monday’s study did not find that climate change had a major influence on the number of smoke-related deaths from Canada’s boreal wildfires.

She suggested that’s likely due to the country’s relatively small population size, and how tricky it is to model forest fires in the region, given its unique mix of shrubs and peat.

But she also noted that a stretch of devastating Canadian wildfire seasons over the past several years was not captured in the study, and she expects future research could find a bigger increase in deaths and public-health problems linked to climate change.

The most affected regions in the study were South America, Australia and Europe.

Kou-Giesbrecht said the more studies that uncover the link between climate change and disasters as “tangible” as wildfires, the more the case for “drastic climate action” will be bolstered.

“I think that the more and more evidence that we have to support the role of climate change in shaping the past 100 years, and knowing that it will continue to shape the next 100 years, is really important,” she said.

“And I find that personally interesting, albeit scary.”

The study used three highly complex models to estimate the relationship between climate change, land use and fire.

The models, which each contain thousands upon thousands of equations, compare what wildfires look like in the current climate to what they may have looked like in pre-industrial times, before humans started to burn vast amounts of fossil fuels.

The researchers used the models to calculate gas and aerosol emissions from wildfires between 1960 and 2019, and then make estimates about annual smoke-related deaths.

The type of methodology used by Monday’s studies, known as attribution science, is considered one of the fastest-growing fields of climate science. It is bolstered in part by major strides in computing power.

This report by The Canadian Press was first published Oct. 21, 2024.

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Some Ontario docs now offering RSV shot to infants with Quebec rollout set for Nov.

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Some Ontario doctors have started offering a free shot that can protect babies from respiratory syncytial virus while Quebec will begin its immunization program next month.

The new shot called Nirsevimab gives babies antibodies that provide passive immunity to RSV, a major cause of serious lower respiratory tract infections for infants and seniors, which can cause bronchiolitis or pneumonia.

Ontario’s ministry of health says the shot is already available at some doctor’s offices in Ontario with the province’s remaining supply set to arrive by the end of the month.

Quebec will begin administering the shots on Nov. 4 to babies born in hospitals and delivery centers.

Parents in Quebec with babies under six months or those who are older but more vulnerable to infection can also book immunization appointments online.

The injection will be available in Nunavut and Yukon this fall and winter, though administration start dates have not yet been announced.

This report by The Canadian Press was first published Oct. 21, 2024.

-With files from Nicole Ireland

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.

The Canadian Press. All rights reserved.

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