A senior scientific adviser has said more data is needed before the government can adopt a proposal to give as many people as possible a single dose of a Covid vaccine rather than preserving stocks so there is enough for a second jab.
The former prime minister Tony Blair and Prof David Salisbury, a former director of immunisation at the Department of Health, backed the idea on Wednesday, saying second shots should be given only when more stock is available.
While the suggestion would mean each vulnerable person who has received the vaccine would be afforded less protection, the number of people given at least some protection would double.
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 the Labour committee member Graham Stringer that any such change to the established vaccine policy was “too risky”.
Blair told BBC Radio 4’s Today programme earlier that the proposal to spread the doses of the Pfizer/BioNTech 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”.
Quick GuideHow 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
He said the Oxford/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 10m or 20m doses of the vaccine, you vaccinate 10 or 20 million 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.”
Salisbury told the Guardian: “In the circumstances we currently face, I think the best use of the vaccine stocks is to give the first dose to as many high-risk people as possible. And after that, you then give second doses.”
He said the New England Journal of Medicine study had reported the first dose of the Pfizer/BioNTech vaccine to have 91% efficacy, compared with 95% for two doses. That level of protection, he said, was justification for administering only one dose to a larger group at first, followed by the second when possible.
While the study showed 52% efficacy in the period between the first and second doses, Salisbury explained that each dose only begins to take effect after several days. Therefore, he interpreted data from the period immediately after the second dose as indicative of the possible efficacy of the first.
The study’s authors noted, however, that it was not “designed to assess the efficacy of a single-dose regimen”. Prof Stephen Evans, of the London School of Hygiene and Tropical Medicine, said a briefing document produced by the US Food and Drug Administration was a “more reliable source”.
He said: “What is clear is that there is evidence of efficacy in the short term and it seems likely that the efficacy will not decline notably. This efficacy is clearly nearer 80% than 90% and could be quite a bit lower, but is still good.”
A Department of Health and Social Care spokesperson said: “Our brilliant NHS has vaccinated more than half a million people against Covid-19 using the Pfizer/BioNTech vaccine. Over the coming weeks and months, the rate of vaccinations will increase as more doses become available and the programme continues to expand.”