Can we mix and match the vaccines? A big question for two doses of COVID-19 – fr

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Can we mix and match the vaccines? A big question for two doses of COVID-19 – fr


TORONTO – If your first vaccine was done by one company, can you get a different vaccine for your second vaccine?

Scientists are looking to answer this question for the first time, and a new study in the UK may provide guidance soon.

The concept has been dubbed ‘mix and match’ – using different combinations of COVID-19 vaccines approved for the first and second doses in a single person.

Questions about vaccine supply, as well as concerns about specific vaccines, have put some urgency behind the quest to see if it works.

“You won’t be able to control the supply in the first and second doses, maybe like some other countries,” said Matthew Snape, professor at the University of Oxford and lead researcher on the study. British. “So these mixed schedules just might be the key to delivering two doses to as many people as possible around the world.”

Led by the Oxford Vaccine Group, the COM-COV study was launched in February and the results of the first phase – which involved more than 800 volunteers over the age of 50 – are expected to be published in a few weeks.

Taking doses of different vaccines should be safe, experts say, so the most important question is whether vaccines still work when combined.

But it’s not just about mixing vaccines to increase supply.

The UK study can also determine whether two different shots produce a better result than a single brand.

Some test subjects are given a dose of AstraZeneca, which uses a cold virus to boost immunity, and a dose of Pfizer, which prime the immune system with messenger RNA.

When the researchers expanded the study in April, they added Moderna and Novavax to any vaccines the volunteers might receive.

The volunteers were given vaccines at random, with some receiving the same vaccine in their first and second dose to serve as a control group to see if the mixture of vaccines produced a different immune response.

Previous animal studies suggest that using vaccine combinations produces long-lasting antibodies against coronavirus infections, experts say.

“We also know, through immunology experiments in animal models, that sometimes mixing and matching vaccines gives you better protection, because each vaccine has its own attributes,” said Tania Watts, professor of immunology at University of Toronto at CTV News.

According to the results of the UK study, a ‘mix and match’ strategy could present a new option for those who received Astra Zeneca for their first dose and who are now concerned about supply shortages or the rare side effects of blood clotting.

As much of AstraZeneca is made in India, which is currently badly affected by the virus, concerns have been raised in provinces such as British Columbia, where tens of thousands of people have been given AstraZeneca as their first dose, that the second doses will not arrive within the four month withdrawal period recommended by NACI.

“I really hope that by the end of the month we can start seeing data from Oxford so that [we] can make an informed decision about it, ”Watts said.

We are in an “unprecedented” situation with the pandemic, Watts said, and that prompts us to ask new questions.

“We must do all we can to provide the best response,” she said, adding that this research could “inform the deployment of vaccines against other diseases for years to come”.

The UK is not the only place to study this concept. There are already “mixes and matches” happening in Canada in Quebec, as a strategy to increase the number of people fully vaccinated.

In April, Quebec announced it would replace the Pfizer vaccine for some long-term care residents who had received Moderna as their first vaccine, in order to immunize residents more quickly in the face of variants and supply shortages.

Pfizer and Moderna are more similar than some of the other vaccines because both are mRNA vaccines.

Dr Sophie Zhang, chief medical officer of 15 long-term care facilities in Montreal, said they had no plans to mix the doses but had responded to a lack of supplies.

“There was a delay in the arrival of the shipments of Moderna, and we decided that it was urgent to give them the second dose, and that we were ready to give them a dose of another type of vaccine more quickly. instead of waiting for the Moderna supplies to arrive, ”she said.

She said about half of the care homes where she works have received mixed doses, covering around a few hundred people.

“I think there is what we would do in an ideal world when there is no shortage, and there is no emergency, and then there is what we would do when we have a crisis situation, ”said Zhang.

She said they were watching closely for side effects, but didn’t notice anything out of the ordinary.

“In terms of security, I think so far we have no worries or concerns,” she said. “Maybe in the future it will even be something that will be recommended because it might even boost the immune response.”

And CTV News has learned that Canada will launch its own larger study on “mix and match” vaccines – with more details to come.

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