Is there an advantage to receiving multiple COVID-19 vaccines?


TORONTO – Dozens of COVID-19 vaccine candidates are currently in advanced stage testing, with two pioneers from Pfizer and Moderna showing promising efficacy. But if multiple vaccines are finally approved in Canada, a possibility that researchers say could occur as early as next year, experts say there will be no added benefit to getting several different vaccines.

Infectious disease specialist Dr Sumon Chakrabarti said there was no medical benefit to taking more than one vaccine.

“They’re the same kind of mechanism in terms of how they work, so I think either one would be beneficial,” he said.

Dr. Eleanor Fish, professor of immunology at the University of Toronto, agreed. She mentioned the Moderna and Pfizer vaccines, which both aim to induce an immune response against the same viral target: the spike protein, which interacts with other proteins on human cells to encourage virus replication.

“The two flagship vaccines appear to be over 90 (percent) effective, so just as effective,” she told Tuesday.

Moderna said on Monday his shots appeared to be 94.5 percent effective, according to preliminary data from an ongoing study. The announcement came a week after Pfizer said its vaccine appeared to be 90% effective, based on early but incomplete testing.

While Moderna appears to offer a bit more protection, at least from preliminary results, Chakrabarti said the difference probably wouldn’t be noticeable in a real context.

“Ninety-five percent versus 90 percent is a difference. But I think that at the level of the population, it is not a big problem, ”he declared.

Even when multiple vaccines are approved, Fish said Canadians likely won’t be able to choose which one to take.

“I suspect that choice will not be a problem when the vaccines arrive in Canada. There will be a strategy to roll out vaccination, prioritizing the most vulnerable and frontline workers, ”she said.

The back-to-back announcements from Pfizer and Moderna sparked optimism among scientists and prompted an immediate reaction in the stock market, with the CEO of Pfizer selling $ 5.6 million in shares on the day he broke the news and airlines benefiting from a boost.

The two companies have signed agreements with the federal government for more than 20 million doses and have asked Health Canada to review their products once ready. In total, the federal government has committed to purchasing more than 100 million doses from several different companies, including Johnson & Johnson and Novavax Inc.

Rather than betting on the success of a business, the federal government has spread its investments in hopes of getting the first successful COVID-19 vaccine as soon as possible. However, in order to immunize as many Canadians as possible, it will be necessary to have a variety of effective doses available and the ability to do more.

The government has also pledged $ 126 million to build a facility capable of producing up to two million doses of any potential vaccine per month.

Dr Isaac Bogoch, an infectious disease specialist, said people will take a vaccine initially once vaccination programs are started. After that, he said, there are still many unanswered questions about what will happen next.

“It is currently not known how long the immunity will last after vaccination and, if revaccination is needed, what vaccines will be offered to people,” he told on Tuesday.

Among these unanswered questions is how vaccines will be transported. Pfizer vaccine should be stored at ultra-low temperatures of -70 C, which could make transport difficult, especially to developing countries in hot climates. Moderna’s vaccine can be stored at -20 ° C, which the company said could be achieved through a regular freezer and eliminate storage problems.

With thousands of new cases reported in Canada every day, a safe and effective vaccine has long been a primary goal of public health officials. Kelly Grindrod, an associate professor at the University of Waterloo’s school of pharmacy, said the hope was that Canada could start administering vaccines to frontline healthcare workers in early 2021.

“Right now there needs to be a broad definition of ‘front line’ to ensure that we include doctors, nurses and pharmacists, but also those in low-paying health care positions who have high infection rates, such as personal support workers, orderlies. and the hospital cleaning staff, ”she said in a statement.

“By having a broad definition of ‘health worker’, the first vaccines would reach the hardest-hit communities first.”

But even though Canada approves and distributes millions of vaccines, experts have long warned that a vaccine will not end the pandemic immediately. World Health Organization spokeswoman Margaret Harris stressed that vaccines do not completely eliminate disease.

“We have a lot of great vaccines against other diseases, but we still have the diseases,” Harris said Tuesday on Your Morning.

“So people need to understand that it’s a great tool and it’s being used widely and judiciously, if it gets to all the people who need it at the same time it will make a difference. But we also need to take whatever public health measures work. ”

While waiting for a vaccine or vaccines to become available, health experts advise Canadians to follow the same rules: wear a mask, practice social distancing and wash their hands often. As of Tuesday morning, more than 302,000 people in Canada contracted COVID-19 and more than 11,000 died.

With files from the Canadian Press


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