Debate rages over wisdom of Britain’s new ‘single jab’ Covid vaccine strategy

Scientists across the world were locked in fierce debate on Friday over the wisdom or otherwise

Scientists across the world were locked in fierce debate on Friday over the wisdom or otherwise of the UK switching to a single dose strategy for Covid-19 vaccines.

White coats were flapping on social media after the Joint Committee on Vaccination and Immunisation (JCVI) published its rationale for the move on Thursday night.

“The advice … is aimed at maximising protection in the population”, said the JVCI.

“Given the high level of protection afforded by the first dose, models suggest that initially vaccinating a greater number of people with a single dose will prevent more deaths and hospitalisations than vaccinating a smaller number of people with two doses”.

The move to prioritise first jabs of the vaccines was initially proposed by former prime minister Tony Blair. There is little doubt it is an innovation, though some prefer the word gamble.

Vaccine supply is horribly tight. At the same time, people are again dying in significant numbers from and modelling suggests the only way of keeping the death toll below last April’s peak is to get vaccines into people’s arms, and fast.

“Given the epidemiology of COVID-19 in the UK in late 2020 there is a need for rapid, high levels of vaccine uptake amongst vulnerable persons”, concluded the JVCI. 

“Initially prioritising delivery of the first vaccine dose [will] reduce the number of preventable deaths from COVID-19”.

The move is a pragmatic one; an act of brinksmanship. It has been cast as both a welcome example of not allowing the perfect get in the way of the good and as “a desperate measure for a desperate time”.

Criticism of the strategy takes different forms. Eric Topol, a senior US physician, took a purist view. Tweeting yesterday morning to his  363,000 followers who include many of the world’s leading doctors and scientists, he wrote: “How to spoil phenomenal results of the most important clinical trials of our generation: 1/ Extrapolate from 2-dose trials in >75,000 participants who all got 2 doses that 1-dose works fine”.

Others focused in on the detail. While there is trial data to support the second dose of the Oxford-AstraZeneca jab being given after 12 weeks, the same is not true of the Pfizer vaccine.

“The application of the same principle to the Pfizer/BioNtech vaccine is more difficult to evaluate”, tweeted Deepti Gurdasani, a senior lecturer in Epidemiology and statistical genetics at Queen Mary University of London. “This vaccine was studied with a strict protocol of 21 days between doses and the company has since issued a warning that they cannot ensure efficacy if [the] protocol is changed”.

British regulators accept there is a degree of risk, but think it small. Sandy Douglas, a senior researcher on the Oxford vaccine team, agrees.

Can we extrapolate from the Pfizer trial data that it too will work after 12 weeks?, he asked on Twitter yesterday before answering his own question.

“It’s a judgment call. On one hand is evidence-based medicine’s scepticism of anything not directly proven ‘beyond reasonable doubt’ in a Random Controlled Trial; on the other is a ‘balance of probabilities’ approach based upon the biology.

“Based upon the biology, I’d eat my hat if the Pfizer vaccine is substantially less effective with a longer dose interval. Most vaccines induce stronger immune responses with longer intervals.”

Others raised practical considerations. Azeem Majeed, a professor of primary care and public health at Imperial College London and a practising GP, told the Guardian newspaper he was shocked by the change of plan.

“We’ve got thousands or perhaps tens of thousands of people who have already booked their second jabs, and these are people who are all elderly, so they often have to make special arrangements for their care or have someone to bring them down”. 

The JVCI only advises ministers and, ultimately, the new strategy will have been the Prime Minister’s call. It will not have been an easy one as it is not without some risk.

But given the dire circumstances the country finds itself in, it is hard to imagine any politician jumping the other way. At stake are about 50,000 lives, the latest modelling suggests. If they can be protected with early vaccination, the gamble will have been worth taking.

The nightmare scenario is that a partial vaccination causes the virus to mutate even more rapidly. 

“Is it just me or does uncontrolled, high level community transmission with circulation of several new #SARSCoV2 #COVID19 variants while starting vaccination with modified schemes, leading to partial immunity in a large proportion, sound like a bad idea?”, asked Prof Isabella Eckerle, a virologist at the Geneva Centre for Emerging Viral Diseases.

The longer this crisis goes on the clearer it becomes that countries which moved to suppress the virus early have less to worry about today.

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