After initially saying AstraZeneca’s COVID-19 vaccine shouldn’t be given to people above the age of 65, the National Advisory Committee on Immunization (NACI) reversed its stance on Tuesday, announcing that the vaccine was safe for seniors.
The news comes as several countries around the world have temporarily paused their rollout of AstraZeneca’s doses and the Canadian government tries to quell fears about its safety emanating from reports of blood clots and apparent confusion over the vaccine’s safety.
“People can can get confused quite easily, especially if recommendations change,” said Dr. Saverio Stranges, who chairs Western University’s department of epidemiology and biostatistics.
But “we also need to acknowledge that science evolves, especially in the midst of a pandemic where we are creating new information all the time.”
How did we get here?
The decision was a sharp reversal of guidelines made earlier this month, which advised against giving the vaccine to seniors because of “limited information on the efficacy of this vaccine in this age group” at that time.
However, now there is enough “real-world evidence” to show the vaccine is safe for seniors, Dr. Caroline Quach-Thanh, who chairs NACI, announced on Tuesday.
The AstraZeneca vaccine became the third COVID-19 shot authorized for use by Health Canada in anyone 18 years or older in late February, joining mRNA vaccines from Pfizer-BioNTech and Moderna.
Results from AstraZeneca’s clinical trials demonstrated an average efficacy of approximately 62 per cent in participants ranging from 18 to 64 years old.
Canada has inked a deal with the Serum Institute in India to manufacture two million doses of the AstraZeneca vaccine, which have already begun to arrive. Another 20 million doses already secured with AstraZeneca will start shipping in the spring.
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Why the change, NACI?
Those at higher risk of severe illness, death and exposure should be prioritized for mRNA COVID-19 vaccines made by Pfizer-BioNTech and Moderna, however Quach-Thanh said AstraZeneca is on par with the mRNA vaccines when it comes to real-world effectiveness after just a first dose.
New studies from the U.K., which has administered the AstraZeneca vaccine to tens of thousands of citizens already, demonstrated the doses were safe and effective in older adults, she said, including “in adults over the age of 80 with significant medical comorbidities.”
Dr. Matthew Tunis, executive secretary to NACI, said future changes could come “days after a decision” has been announced if better evidence emerges.
“It might be that the evidence comes days after a decision. It might be weeks after a decision or months. We have no control over where the data is coming from and it’s impossible to predict the future,” he said.
In one pre-print of a study referenced by Quach-Thanh, a single dose of the AstraZeneca vaccine reached an effectiveness of 70 per cent in participants aged 80 years and older between 28 and 34 days before plateauing. Two weeks after receiving a second dose, researchers said the vaccine’s effectiveness rose to 89 per cent.
The study, published in medxRxiv, found similar results in participants at least 70 years old. Those who had received their first shot saw vaccine effectiveness reach 61 per cent before plateauing between 28 and 34 days after being administered the first shot. That number increased to 73 per cent 28 to 34 days after receiving their booster injection.
Director of the Bureau of Medical Science at Health Canada Dr. Marc Berthiaume also weighed in.
He said information reviewed by the agency showed the number of “thromboembolic adverse events,” which are blood clots formed due to blood changes, were lower than would be expected.
“Overall, Health Canada considers that the benefits of the vaccines, considering the risk of contracting COVID infection and its associated complications, outweigh any risk that (could) potentially be associated with the vaccine,” he said.
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Addressing vaccine hesitancy
Social media like Instagram and Twitter have made it easier for officials to get their messages across, but Stranges said it has also made it easier for misinformation to filter through, and for officials’ advice to get misconstrued.
“It’s a difficult scenario because people get information from the sources they feel more comfortable with, and those sources are not necessarily official, public health sources,” he said.
Experts have expressed concerns the sudden change in guidance has only added contention to the negative image of AstraZeneca’s vaccine, which has been mired by suspicions that it may cause blood clots.
A slew of European countries have temporarily suspended use of the vaccine after reports surfaced of people suffering from embolisms formed by blood clots who had recently received the shot.
In a review of more than 17 million people who have received the vaccine across the EU and Britain, AstraZeneca said it found 37 cases of blood clots.
“Obviously you assess that there is a correlation between that specific event and the vaccination, but the correlation does not necessarily mean that there is a causal link,” said Stranges.
According to AstraZeneca, this number is no larger than what is expected within a general population. However, Dr. Sumon Chakrabarti, an infectious disease physician at Trillium Hospital in Mississauga, Ont., said facts will hold little sway with people whose hesitancy is rooted in mistrust.
He cautioned against “beat(ing) people over the head with facts.”
“Sometimes data and facts is not what people want,” Chakrabati said.
“They want the truth, of course, but they also just want the reassurance…. Sometimes it is just fear, sometimes it’s mistrust of the government, or some people in general are mistrustful of any kind of medical therapy or the medical field in general.”
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Zain Chagla, an infectious disease specialist at Hamilton’s St. Joseph’s Hospital, noted that “even if all of the dust settles on all of this stuff and it’s (proven) effective in 65-year-olds and it’s actually 80 per cent effective and there’s no clot risk, you’ve already introduced three strikes that are hard to wash away from people who are already hesitant to take this vaccine over Moderna and Pfizer.”
The reports have triggered an investigation led by The European Medicines Agency (EMA), which is expected to release its results on Thursday. In the meantime, the EMA has urged governments not to halt the use of the vaccine, claiming it is still “firmly convinced” that the “benefits” of the vaccine “outweigh” the risks.
The results of the investigation are expected Thursday.
Dr. Horacio Bach, an infectious disease specialist teaching at the University of British Columbia, emphasized how important it is the public understand that there is no evidence that the AstraZeneca vaccine causes blood clots, or would be harmful to seniors. He encouraged Canadians to get vaccinated as quickly as possible.
“It’s very important that at this stage in the middle of a pandemic, everyone should take whatever is available,” he said.
“The more people (who) vaccinate, the less chance the virus (has) to find a new host, meaning a new person, (to) infect.”
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