The head of the British government task force said the trial will likely begin in January to see if mixing and matching COVID vaccines provides better protection than two doses of the same dose.
How does the Pfizer / BioNTech Covid-19 vaccine work?
Pfizer / BioNTech Covid jab is a mRNA vaccine. Basically, mRNA is a molecule that living cells use to convert the gene sequences in DNA into proteins that are the building blocks of all their basic structures. A portion of the DNA is transcribed (“transcribed”) into a piece of messenger RNA, which is in turn “read” by the cell’s tools to make proteins.
In the case of an mRNA vaccine, the mRNA of the virus is injected into a muscle, and then our cells read it and make the viral protein. The immune system reacts to these proteins – which cannot cause disease by themselves – just as if they were transferred to the entire virus. This generates a protective response that studies indicate continues for some time.
The first two Covid-19 vaccines to announce results from phase III trials were based on mRNA. They were the first to block because once the genetic code for Sars-CoV-2 was known – published by the Chinese in January 2020 – companies that were working on the technology were able to start producing mRNA for the virus. Conventional vaccines take longer to make.
Adam Finn, Professor of Pediatrics at Bristol Children’s Vaccination Center, University of Bristol
The trial will begin if the University of Oxford / AstraZeneca vaccine is approved in the coming weeks, as hoped. Treatment can only be given with licensed vaccines.
The news comes as the first British patients start receiving vaccinations against the Corona virus from Tuesday, a blow by Pfizer / BioNTech, a week after the United Kingdom became the first country in the Western world to approve a Covid vaccine.
Those who participate in the January trial will receive one injection of AstraZeneca and one injection of Pfizer. A vaccine from US biotechnology company Moderna will also be included if approved.
Both Pfizer and Moderna vaccines have been shown to be 95% effective in protecting people from the virus. For AstraZeneca, the efficacy was 62% among the largest two-dose group, but it increased to 90% among the smaller group given a half dose initially, followed by a full dose.
Kate Bingham, the outgoing chair of the UK Vaccine Task Force, said the “mix-and-match” experiments are not about making the limited supply of vaccines go any further. The UK government has requested 40 million doses of the Pfizer vaccine and 100 million doses of the Oxford / AstraZeneca filter.
“It’s not happening because of the supplies,” Bingham said. “It’s about trying to stimulate the immune response and toughness and has nothing to do with the vaccines we have.”
The concept is known as a heterogeneous master batch. “That means mixing and matching vaccines,” Bingham said. “So you do first with one vaccine, then the second – whether it’s 28 days or two months, or whatever the agreed periods are – will be with a different vaccine.”
Viral vaccines such as the Oxford vaccine, which is based on the common cold virus of chimpanzees, gives a much greater cellular response – forcing T cells to kill cells infected with the coronavirus. MRNA vaccines, such as Pfizer vaccines, tend to generate a greater antibody response. So the idea is to combine them, in any arrangement, to help the immune system respond more strongly to Sars-CoV2.
“No one has done this live, and since we’re going to have safe vaccines, we have to do this study, because then we have the ability to produce better immune responses,” said Cliff Dix, Vice President of the Task Force.
“There is a slight benefit to it as well, in that if the exercise is basic and reinforces either way around work, it might help spreading, because it might be easier to spread that way, but the main reason is to get an immune response.”
Bingham and Dicks were speaking at the launch of a progress report on the first six months of the task force, which clinched deals for seven different vaccines for the UK.
Three of them – Oxford / AstraZeneca, Valneva and Novavax – are manufactured in the UK. The first doses of the AstraZeneca vaccine were manufactured in the Netherlands and Germany, but there are 4 million doses already in the country and most of the remaining supplies will be manufactured in the United Kingdom.
There are still questions about when the Oxford / AstraZeneca vaccine will be approved. The government required the UK regulator to evaluate it after a periodic review, and to evaluate all data and information regarding safety, efficacy and product quality in the last months when it became available. But the full data from clinical trials in the late stages, which included 24,000 people, has not yet been published, and it is not known how regulators will present the results.
Dicks said the staff did not regret supporting other types of vaccines on mRNA vaccines such as Pfizer and Moderna, adding: “We certainly didn’t have enough. [of the Pfizer vaccine] To vaccinate everyone. “
They looked at Moderna but realized they couldn’t get any doses until April, so they didn’t sign a contract. On the day Moderna announced its results, a deal was agreed to buy 5 million doses, which were later increased to 7 million doses.
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