More data needed if second vaccine dose is diverted to first-timers, says Covid adviser | Coronavirus

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A senior government scientific adviser has said more data is needed before a proposal to give as many people as possible an initial dose of a Covid vaccine rather than preserving stocks so there is enough for a second jab, is adopted.

The former prime minister Tony Blair and Prof David Salisbury, a former director of immunisation at the Department of Health, have backed the plan. Each person requires two doses to boost effectiveness, but they said the limited existing stocks should be used to administer only a single dose to twice as many people, with the second shot given only when more stock is available.

While the suggestion would mean each vulnerable person who received the vaccine would be afforded less protection, the number who were given at least some would double.

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How does the Pfizer/BioNTech Covid-19 vaccine work?

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The Pfizer/BioNTech Covid jab is an mRNA vaccine. Essentially, mRNA is a molecule used by living cells to turn the gene sequences in DNA into the proteins that are the building blocks of all their fundamental structures. A segment of DNA gets copied (“transcribed”) into a piece of mRNA, which in turn gets “read” by the cell’s tools for synthesising proteins.

In the case of an mRNA vaccine, the virus’s mRNA is injected into the muscle, and our own cells then read it and synthesise the viral protein. The immune system reacts to these proteins – which can’t by themselves cause disease – just as if they’d been carried in on the whole virus. This generates a protective response that, studies suggest, lasts for some time.

The two first Covid-19 vaccines to announce phase 3 three trial results were mRNA-based. They were first off the blocks because, as soon as the genetic code of Sars-CoV-2 was known – it was published by the Chinese in January 2020 – companies that had been working on this technology were able to start producing the virus’s mRNA. Making conventional vaccines takes much longer.

Adam Finn, professor of paediatrics at the Bristol Children’s Vaccine Centre, University of Bristol

But Prof Wendy Barclay, a member of the government’s New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), told the Commons science and technology committee: “I think that the issue with that is that the vaccine is on the basis of being given two doses, and the efficacy is on that basis.

“To change at that point, one would have to see a lot more analysis coming out from perhaps the clinical trial data.”

Barclay agreed with the suggestion of Labour’s committee member Graham Stringer that any such change to the established vaccine policy was “too risky”.

Blair had told BBC Radio 4’s Today programme on Wednesday morning that the proposal to spread the doses of the Pfizer vaccine already in the government’s possession more widely and thinly should be considered because “the reality is, we are now in severe lockdown until vaccination”.

He said the AstraZeneca vaccine, which is expected to be approved this month and is easier to store and transport, could then be used in the same way once it becomes available.

“Does the first dose give you substantial immunity, and by that I mean over 50% effectiveness? If it does, there is a very strong case for not, as it were, holding back doses of the vaccine,” Blair said.

“If, in January, AstraZeneca is delivering you 10 or 20m doses of the vaccine, you vaccinate 10 or 20m people because then you should get more vaccine coming on stream by the time you are ready for the second dose and that first dose can give you substantial immunity.”

The former prime minister also criticised the “somewhat inflexible ‘by age’ structure” used to determine who receives the jab.

Experts at the Joint Committee on Vaccination and Immunisation have drawn up a priority list based on clinical need. But Blair, who does not have a medical background, said “there is a strong case for saying you have got to focus also on the people spreading the disease, not simply the most vulnerable”.

The Department of Health and Social Care has not responded to a request for comment.

Hafta Ichi
Source: The Guardian
Keyword: More data needed if second vaccine dose is diverted to first-timers, says Covid adviser | Coronavirus

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