Scientists think they've discovered why the AstraZeneca COVID-19 vaccine can cause rare blood clots
Scientists in the U.K. believe they have discovered the reason why some people experienced the very rare side-effect of blood clots after receiving the AstraZeneca COVID-19 vaccine.
The findings, published in the journal Science Advances on Wednesday, reveal that a protein found in blood is drawn to a component of the vaccine, which triggers a reaction from the body’s immune system that can result in clots.
The AstraZeneca vaccine, like other viral vector vaccines, uses a safe virus as a “host” to deliver genetic information about the COVID-19 spike protein to the vaccine recipient's cells so that they can build an immune response and create antibodies.
The AstraZeneca COVID-19 vaccine uses a cold virus from a chimpanzee, also known as a chimpanzee adenovirus, as the delivery system. This is because it cannot make humans sick – and, because they have not been exposed to it before, they will not have antibodies against it.
Viral vector vaccines modify the delivery virus so that it cannot spread, they simply delivers the instructions for the body’s cells.
By analyzing the chimpanzee adenovirus used by AstraZeneca with cryo-electron microscopy, which allows for molecular-level details to be seen, researchers found that the adenovirus attracts the blood protein known as “platelet factor 4” to it.
Cryo-electron microscopy involves flash-freezing the study subject and then bombarding them with electrons to produce microscope images of individual molecules. Those are then used to reconstruct the structure of the subject in minute detail.
The cryo-electron microscopy image of the chimpanzee adenovirus, which is less than 100 nanometres across, that delivers the Oxford-AstraZeneca vaccine. (Science Advances Journal)
The cryo-electron microscopy image of the chimpanzee adenovirus which delivers the Oxford-AstraZeneca vaccine. (Science Advances Journal)
Platelet factor 4 is implicated in the origins of another clotting event called heparin-induced thrombocytopenia (HIT), which causes changes to the blood that may cause a clot to form in the blood vessels.
Researchers posit that the body begins to attack the platelets that are attached to the adenovirus, after mistaking it as part of the foreign virus. Then, when antibodies are released into the bloodstream to attack, they clump together with the platelet factor 4 and can form a dangerous blood clot known as vaccine-induced thrombotic thrombocytopenia or VITT.
Because that sequence of events in the body is so specific, it may explain why the development of blood clots after receiving the vaccine is such a rare phenomenon.
The U.K. findings echo a Canadian study conducted by researchers at McMaster University in Hamilton, Ont., and published this July in the scientific journal Nature.
In the Canadian study, researchers analyzed blood samples from five patients with VITT and compared them to blood samples of 10 patients with HIT and 10 samples from healthy individuals.
Looking at the amino acids of the interaction between the VITT antibodies and platelet factor 4 protein, researchers found eight specific amino acids on the platelet protein that were identical to the binding site of HIT, which they believe could explain the similar patterns in how the blood clots form after vaccination.
However the U.K. study was able to render the highest resolution of the adenovirus used in the AstraZeneca COVID-19 vaccine to date, allowing them to better understand its primary cell attachment proteins and its structure.
VITT has been linked to at least one death in Canada after an Ontario man received the AstraZeneca vaccine in May, and to 73 deaths out of close to 50 million doses of AstraZeneca administered in the U.K.
The Public Health Agency of Canada’s National Advisory Committee of Immunization stopped recommending AstraZeneca’s COVID-19 vaccine as a second dose option after some Canadian recipients reported blood clots in the spring of 2021.
Researchers in the U.K. hope their study findings can be used to improve future vaccines and reduce the risk of blood clots.
-----
With files from CTVNews.ca writer Brooklyn Neustaeter
COVID-19 COVERAGE
CTVNews.ca Top Stories
'Hurts like hell': What goes into the price of gas in Canada
With the price of gas rising above $2 per litre and setting new records in Canada this year, CTVNews.ca looks at what goes into the price per litre of gasoline and where the situation could go from here.
'This is an unusual situation': Feds monitoring monkeypox cases in Canada
Canada's Chief Public Health Officer Dr. Theresa Tam says the federal government is monitoring monkeypox cases and their chains of transmission after two cases were confirmed in this country.
Russia claims to have taken full control of Mariupol
Russia claimed to have captured Mariupol on Friday in what would be its biggest victory yet in its war with Ukraine, following a nearly three-month siege that reduced much of the strategic port city to a smoking ruin, with over 20,000 civilians feared dead.
'Fight for a stronger Alberta': Kenney comments for first time since announcing resignation
Premier Jason Kenney spoke publicly Friday for the first time since dropping the bombshell announcement that he plans to step down as UCP leader and premier of Alberta.
Ontario woman says daughter was discriminated against over face mask
An Ontario woman believes her daughter was discriminated against after she was allegedly kicked out of a local activity centre over her choice to wear a face mask.
WHO calls emergency meeting as monkeypox cases cross 100 in Europe
The World Health Organization was due to hold an emergency meeting on Friday to discuss the recent outbreak of monkeypox, a viral infection more common to west and central Africa, after more than 100 cases were confirmed or suspected in Europe.
NEW | Decision to ban Huawei and ZTE from 5G wasn't easy, PM Trudeau says
On the heels of news that Canada is banning Huawei Technologies and ZTE from participating in the country’s 5G wireless networks, Prime Minister Justin Trudeau said the decision wasn't easy to make. The prime minister also defended the timing of the decision, saying that while it will be years before all use of products from these Chinese companies will be outlawed, it's happening before the country is even more interconnected by the next-generation telecommunications infrastructure.
Costs reach $25.6 million for public inquiry into 2020 mass shooting in Nova Scotia
The public inquiry into Nova Scotia's mass shooting has already cost $25.6 million to investigate the April 18-19, 2020, rampage -- and there are still about five months remaining in its mandate.
Quebec City Halloween attacker found guilty of first-degree murder
A man who used a sword to kill and maim victims in Quebec City's historic district on Halloween night 2020 has been found guilty of murder.
Canada
-
'This is an unusual situation': Feds monitoring monkeypox cases in Canada
Canada's Chief Public Health Officer Dr. Theresa Tam says the federal government is monitoring monkeypox cases and their chains of transmission after two cases were confirmed in this country.
-
Why Canada is banning Huawei from participating in Canada's 5G network
The federal government is banning China's Huawei Technologies from involvement in Canada's 5G wireless network. Huawei and the Chinese government have vigorously denied accusations around the danger of spying, saying that the company poses no security threat.
-
After N.B. police killing of Indigenous woman, chiefs demand systemic racism inquiry
The results of the recent coroner's inquest into the police killing of an Indigenous woman in New Brunswick demonstrate the urgent need for an Indigenous-led inquiry into systemic racism, according to the six chiefs of the Wolastoqey Nation.
-
Costs reach $25.6 million for public inquiry into 2020 mass shooting in Nova Scotia
The public inquiry into Nova Scotia's mass shooting has already cost $25.6 million to investigate the April 18-19, 2020, rampage -- and there are still about five months remaining in its mandate.
-
Royal Military College awards posthumous degrees to four cadets killed in Kingston, Ont.
Four Royal Military College cadets who died in a motor vehicle accident in Kingston, Ont. last month were given their degrees posthumously on Thursday and honoured in a memorial put on by friends at the college.
-
Ontario woman says daughter was discriminated against over face mask
An Ontario woman believes her daughter was discriminated against after she was allegedly kicked out of a local activity centre over her choice to wear a face mask.
World
-
UN: 18 million facing severe hunger in West Africa's Sahel
The UN is warning that 18 million people in Africa's Sahel region face severe hunger in the next three months, citing the impacts of Russia's war in Ukraine, the coronavirus pandemic, climate-induced shocks and rising costs.
-
Russia claims to have taken full control of Mariupol
Russia claimed to have captured Mariupol on Friday in what would be its biggest victory yet in its war with Ukraine, following a nearly three-month siege that reduced much of the strategic port city to a smoking ruin, with over 20,000 civilians feared dead.
-
As Biden visits Asia, China launches South China Sea drills
China is holding military exercises in the disputed South China Sea coinciding with U.S. President Joe Biden's visits to South Korea and Japan that are largely focused on countering the perceived threat from Beijing.
-
Secret Service workers for Biden Asia trip sent home
Two U.S. Secret Service employees in South Korea to prepare for U.S. President Joe Biden's visit have been sent home after being involved in a confrontation with locals that led to a police investigation.
-
Days before Oklahoma bans abortion, details still uncertain
With Oklahoma only days away from enacting the toughest state ban on abortion in the U.S., providers were preparing to stop terminating pregnancies as questions remained Friday about enforcing the law's limited exceptions.
-
Iran holds pro-government rallies after price protests turn political
Thousands of supporters of Iran’s clerical establishment, including 50,000 Revolutionary Guards and Basij militia members, rallied on Friday, state media reported, after protests against rising food prices turned political.
Politics
-
NEW
NEW | Decision to ban Huawei and ZTE from 5G wasn't easy, PM Trudeau says
On the heels of news that Canada is banning Huawei Technologies and ZTE from participating in the country’s 5G wireless networks, Prime Minister Justin Trudeau said the decision wasn't easy to make. The prime minister also defended the timing of the decision, saying that while it will be years before all use of products from these Chinese companies will be outlawed, it's happening before the country is even more interconnected by the next-generation telecommunications infrastructure.
-
Russian vodka, caviar and diamonds on new Canadian sanctions list
Foreign Minister Melanie Joly announced a fresh wave of sanctions against Vladimir Putin's regime on Friday including a ban on importing Russian vodka, caviar and diamonds. The ban on the import of certain luxury goods from Russia will tighten the net on the country's elite and covers alcoholic drinks, fish and seafood.
-
Trudeau says government will do 'everything we can' to avoid U.S.-style formula shortage
Prime Minister Justin Trudeau attempted to reassure parents on Friday amid a nationwide shortage of baby formula designed specifically for infants with food allergies.
Health
-
'This is an unusual situation': Feds monitoring monkeypox cases in Canada
Canada's Chief Public Health Officer Dr. Theresa Tam says the federal government is monitoring monkeypox cases and their chains of transmission after two cases were confirmed in this country.
-
Monkeypox outbreak: What is it and how does it spread?
A growing number of countries, including Canada, the U.S., Spain, Portugal, and the U.K, are reporting an unusual outbreak of monkeypox. Here is what we know about this rare virus.
-
African scientists baffled by monkeypox cases in Europe, U.S.
Scientists who have monitored numerous outbreaks of monkeypox in Africa say they are baffled by the disease's recent spread in Europe and North America.
Sci-Tech
-
Pro-Russia online operatives falsely claimed Zelenskyy committed suicide, cybersecurity firm says
Pro-Russia online operatives falsely claimed weeks into Moscow's war against Ukraine that Ukrainian President Volodymyr Zelenskyy had committed suicide, as part of an aggressive effort to dent public morale and undermine the Ukrainian government, U.S. cybersecurity firm Mandiant says.
-
Boeing tries to catch up to SpaceX after plenty of drama
Boeing is hoping for success in it second attempt at an uncrewed test flight of its commercial space craft Starliner, hoping a flawless performance will mend its image as the fallen star of human spaceflight.
-
Why Canada is banning Huawei from participating in Canada's 5G network
The federal government is banning China's Huawei Technologies from involvement in Canada's 5G wireless network. Huawei and the Chinese government have vigorously denied accusations around the danger of spying, saying that the company poses no security threat.
Entertainment
-
Prince William and Kate join Tom Cruise on 'Top Gun: Maverick' red carpet
British royalty and Hollywood royalty came together on the red carpet for the charity premiere of the new Tom Cruise movie, "Top Gun: Maverick," on Thursday night.
-
Rihanna and A$AP Rocky welcome first child
Rihanna and A$AP Rocky have welcomed their first child, a source close to the couple confirmed to CNN.
-
Movie reviews: 'Downton Abbey: A New Era' is plucky film meant for fans
This week, pop culture critic Richard Crouse reviews new movies: 'Downton Abbey: A New Era,' 'The Valet' and 'Men.'
Business
-
Canada inflation: How we compare to other G7 nations
With a meeting of G7 finance ministers underway this week, a CTVNews.ca analysis found that while Canadians are feeling the pain of record-high inflation, among G7 nations we are surpassed by Germany, the U.S., and the U.K.
-
Russia to cut Finland's natural gas in latest energy clash
Russia will cut off natural gas to Finland after the Nordic country that applied for NATO membership this week refused President Vladimir Putin's demand to pay in rubles, the Finnish state-owned energy company said Friday, the latest escalation over European energy amid the war in Ukraine.
-
Stakes are high for farmers as 2022 crop shapes up to be most expensive in history
The stakes are high as Canadian farmers take to the fields to plant 2022's crop, which some are saying could find a place in the record books as 'the most expensive ever.'
Lifestyle
-
Canadians are more sensitive to stress than before the pandemic: report
A new report has found that 46 per cent of Canadians are feeling an increased sensitivity to stress than they were prior to the COVID-19 pandemic, impacting their overall mental health.
-
Ancient gold ring stolen during WWII finds its way back to Greece
A more than 3,000-year-old gold signet ring that was stolen from an Aegean island in World War II, crossed the Atlantic, was bought by a Nobel Prize-winning Hungarian scientist and ended up in a Swedish museum has found its way back to Greece.
-
'Holy grail of all finds': Ottawa boy finds gun while magnet fishing in creek
A 12-year-old Ottawa boy is sharing his story after a magnet fishing trip turned up an unexpected find.
Sports
-
Bach says Russia ban is to protect athletes, not punish them
Russian athletes and officials who have been banned from international sporting events because of the war in Ukraine are being protected rather than punished, International Olympic Committee president Thomas Bach said Friday.
-
Rap superstar J. Cole signs with Toronto basketball team
Rap star Jermaine Lamarr Cole -- better known as J.Cole -- has signed with the Scarborough Shooting Stars of the Canadian Elite Basketball League
-
Oilers, Flames alumni look back at last playoff Battle of Alberta: 'A lot of hate'
The 1991 Battle of Alberta in particular was mean, nasty and downright violent.
Autos
-
Mercedes just sold the world's most expensive car for $142 million
Mercedes-Benz confirmed on Thursday that it recently sold the world's most expensive car. A very rare 1955 Mercedes-Benz SLR coupe that had been kept in the German automaker's collection was sold to a private owner for €135 million, the equivalent of $142 million.
-
Hyundai announces $5.5B electric vehicle plant in Georgia
Hyundai Motor Group confirmed Friday the company will spend $5.5 billion on a huge electric vehicle plant near Savannah that will employ thousands -- a deal Georgia's governor called the largest economic development project in the state's history.
-
Aston Martin cleared of suspicion it copied Red Bull design
Formula One team Aston Martin was cleared of suspicion that it had broken competition rules by allegedly copying a design from a Red Bull car, FIA said Friday.
