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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In a study released publicly on Monday as an unpublished, non-peer-reviewed preprint, a team of researchers from the Israel Institute of Technology, Tel Aviv University and Maccabi Healthcare Services found the viral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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Health Canada approves updated Moderna COVID-19 vaccine

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TORONTO – Health Canada has authorized Moderna’s updated COVID-19 vaccine that protects against currently circulating variants of the virus.

The mRNA vaccine, called Spikevax, has been reformulated to target the KP.2 subvariant of Omicron.

It will replace the previous version of the vaccine that was released a year ago, which targeted the XBB.1.5 subvariant of Omicron.

Health Canada recently asked provinces and territories to get rid of their older COVID-19 vaccines to ensure the most current vaccine will be used during this fall’s respiratory virus season.

Health Canada is also reviewing two other updated COVID-19 vaccines but has not yet authorized them.

They are Pfizer’s Comirnaty, which is also an mRNA vaccine, as well as Novavax’s protein-based vaccine.

This report by The Canadian Press was first published Sept. 17, 2024.

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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These people say they got listeria after drinking recalled plant-based milks

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TORONTO – Sanniah Jabeen holds a sonogram of the unborn baby she lost after contracting listeria last December. Beneath, it says “love at first sight.”

Jabeen says she believes she and her baby were poisoned by a listeria outbreak linked to some plant-based milks and wants answers. An investigation continues into the recall declared July 8 of several Silk and Great Value plant-based beverages.

“I don’t even have the words. I’m still processing that,” Jabeen says of her loss. She was 18 weeks pregnant when she went into preterm labour.

The first infection linked to the recall was traced back to August 2023. One year later on Aug. 12, 2024, the Public Health Agency of Canada said three people had died and 20 were infected.

The number of cases is likely much higher, says Lawrence Goodridge, Canada Research Chair in foodborne pathogen dynamics at the University of Guelph: “For every person known, generally speaking, there’s typically 20 to 25 or maybe 30 people that are unknown.”

The case count has remained unchanged over the last month, but the Public Health Agency of Canada says it won’t declare the outbreak over until early October because of listeria’s 70-day incubation period and the reporting delays that accompany it.

Danone Canada’s head of communications said in an email Wednesday that the company is still investigating the “root cause” of the outbreak, which has been linked to a production line at a Pickering, Ont., packaging facility.

Pregnant people, adults over 60, and those with weakened immune systems are most at risk of becoming sick with severe listeriosis. If the infection spreads to an unborn baby, Health Canada says it can cause miscarriage, stillbirth, premature birth or life-threatening illness in a newborn.

The Canadian Press spoke to 10 people, from the parents of a toddler to an 89-year-old senior, who say they became sick with listeria after drinking from cartons of plant-based milk stamped with the recalled product code. Here’s a look at some of their experiences.

Sanniah Jabeen, 32, Toronto

Jabeen says she regularly drank Silk oat and almond milk in smoothies while pregnant, and began vomiting seven times a day and shivering at night in December 2023. She had “the worst headache of (her) life” when she went to the emergency room on Dec. 15.

“I just wasn’t functioning like a normal human being,” Jabeen says.

Told she was dehydrated, Jabeen was given fluids and a blood test and sent home. Four days later, she returned to hospital.

“They told me that since you’re 18 weeks, there’s nothing you can do to save your baby,” says Jabeen, who moved to Toronto from Pakistan five years ago.

Jabeen later learned she had listeriosis and an autopsy revealed her baby was infected, too.

“It broke my heart to read that report because I was just imagining my baby drinking poisoned amniotic fluid inside of me. The womb is a place where your baby is supposed to be the safest,” Jabeen said.

Jabeen’s case is likely not included in PHAC’s count. Jabeen says she was called by Health Canada and asked what dairy and fresh produce she ate – foods more commonly associated with listeria – but not asked about plant-based beverages.

She’s pregnant again, and is due in several months. At first, she was scared to eat, not knowing what caused the infection during her last pregnancy.

“Ever since I learned about the almond, oat milk situation, I’ve been feeling a bit better knowing that it wasn’t something that I did. It was something else that caused it. It wasn’t my fault,” Jabeen said.

She’s since joined a proposed class action lawsuit launched by LPC Avocates against the manufacturers and sellers of Silk and Great Value plant-based beverages. The lawsuit has not yet been certified by a judge.

Natalie Grant and her seven year-old daughter, Bowmanville, Ont.

Natalie Grant says she was in a hospital waiting room when she saw a television news report about the recall. She wondered if the dark chocolate almond milk her daughter drank daily was contaminated.

She had brought the girl to hospital because she was vomiting every half hour, constantly on the toilet with diarrhea, and had severe pain in her abdomen.

“I’m definitely thinking that this is a pretty solid chance that she’s got listeria at this point because I knew she had all the symptoms,” Grant says of seeing the news report.

Once her daughter could hold fluids, they went home and Grant cross-checked the recalled product code – 7825 – with the one on her carton. They matched.

“I called the emerg and I said I’m pretty confident she’s been exposed,” Grant said. She was told to return to the hospital if her daughter’s symptoms worsened. An hour and a half later, her fever spiked, the vomiting returned, her face flushed and her energy plummeted.

Grant says they were sent to a hospital in Ajax, Ont. and stayed two weeks while her daughter received antibiotics four times a day until she was discharged July 23.

“Knowing that my little one was just so affected and how it affected us as a family alone, there’s a bitterness left behind,” Grant said. She’s also joined the proposed class action.

Thelma Feldman, 89, Toronto

Thelma Feldman says she regularly taught yoga to friends in her condo building before getting sickened by listeria on July 2. Now, she has a walker and her body aches. She has headaches and digestive problems.

“I’m kind of depressed,” she says.

“It’s caused me a lot of physical and emotional pain.”

Much of the early days of her illness are a blur. She knows she boarded an ambulance with profuse diarrhea on July 2 and spent five days at North York General Hospital. Afterwards, she remembers Health Canada officials entering her apartment and removing Silk almond milk from her fridge, and volunteers from a community organization giving her sponge baths.

“At my age, 89, I’m not a kid anymore and healing takes longer,” Feldman says.

“I don’t even feel like being with people. I just sit at home.”

Jasmine Jiles and three-year-old Max, Kahnawake Mohawk Territory, Que.

Jasmine Jiles says her three-year-old son Max came down with flu-like symptoms and cradled his ears in what she interpreted as a sign of pain, like the one pounding in her own head, around early July.

When Jiles heard about the recall soon after, she called Danone Canada, the plant-based milk manufacturer, to find out if their Silk coconut milk was in the contaminated batch. It was, she says.

“My son is very small, he’s very young, so I asked what we do in terms of overall monitoring and she said someone from the company would get in touch within 24 to 48 hours,” Jiles says from a First Nations reserve near Montreal.

“I never got a call back. I never got an email”

At home, her son’s fever broke after three days, but gas pains stuck with him, she says. It took a couple weeks for him to get back to normal.

“In hindsight, I should have taken him (to the hospital) but we just tried to see if we could nurse him at home because wait times are pretty extreme,” Jiles says, “and I don’t have child care at the moment.”

Joseph Desmond, 50, Sydney, N.S.

Joseph Desmond says he suffered a seizure and fell off his sofa on July 9. He went to the emergency room, where they ran an electroencephalogram (EEG) test, and then returned home. Within hours, he had a second seizure and went back to hospital.

His third seizure happened the next morning while walking to the nurse’s station.

In severe cases of listeriosis, bacteria can spread to the central nervous system and cause seizures, according to Health Canada.

“The last two months have really been a nightmare,” says Desmond, who has joined the proposed lawsuit.

When he returned home from the hospital, his daughter took a carton of Silk dark chocolate almond milk out of the fridge and asked if he had heard about the recall. By that point, Desmond says he was on his second two-litre carton after finishing the first in June.

“It was pretty scary. Terrifying. I honestly thought I was going to die.”

Cheryl McCombe, 63, Haliburton, Ont.

The morning after suffering a second episode of vomiting, feverish sweats and diarrhea in the middle of the night in early July, Cheryl McCombe scrolled through the news on her phone and came across the recall.

A few years earlier, McCombe says she started drinking plant-based milks because it seemed like a healthier choice to splash in her morning coffee. On June 30, she bought two cartons of Silk cashew almond milk.

“It was on the (recall) list. I thought, ‘Oh my God, I got listeria,’” McCombe says. She called her doctor’s office and visited an urgent care clinic hoping to get tested and confirm her suspicion, but she says, “I was basically shut down at the door.”

Public Health Ontario does not recommend listeria testing for infected individuals with mild symptoms unless they are at risk of developing severe illness, such as people who are immunocompromised, elderly, pregnant or newborn.

“No wonder they couldn’t connect the dots,” she adds, referencing that it took close to a year for public health officials to find the source of the outbreak.

“I am a woman in my 60s and sometimes these signs are of, you know, when you’re vomiting and things like that, it can be a sign in women of a bigger issue,” McCombe says. She was seeking confirmation that wasn’t the case.

Disappointed, with her stomach still feeling off, she says she decided to boost her gut health with probiotics. After a couple weeks she started to feel like herself.

But since then, McCombe says, “I’m back on Kawartha Dairy cream in my coffee.”

This report by The Canadian Press was first published Sept. 16, 2024.

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

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B.C. mayors seek ‘immediate action’ from federal government on mental health crisis

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VANCOUVER – Mayors and other leaders from several British Columbia communities say the provincial and federal governments need to take “immediate action” to tackle mental health and public safety issues that have reached crisis levels.

Vancouver Mayor Ken Sim says it’s become “abundantly clear” that mental health and addiction issues and public safety have caused crises that are “gripping” Vancouver, and he and other politicians, First Nations leaders and law enforcement officials are pleading for federal and provincial help.

In a letter to Prime Minister Justin Trudeau and Premier David Eby, mayors say there are “three critical fronts” that require action including “mandatory care” for people with severe mental health and addiction issues.

The letter says senior governments also need to bring in “meaningful bail reform” for repeat offenders, and the federal government must improve policing at Metro Vancouver ports to stop illicit drugs from coming in and stolen vehicles from being exported.

Sim says the “current system” has failed British Columbians, and the number of people dealing with severe mental health and addiction issues due to lack of proper care has “reached a critical point.”

Vancouver Police Chief Adam Palmer says repeat violent offenders are too often released on bail due to a “revolving door of justice,” and a new approach is needed to deal with mentally ill people who “pose a serious and immediate danger to themselves and others.”

This report by The Canadian Press was first published Sept. 16, 2024

The Canadian Press. All rights reserved.

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