UK Edition
Vaccines are like buses. You wait for one for ages, then they all come trundling along together, by which time a whole crowd is clamouring to get on board.
But what if a cheaper, less reliable bus arrives during the melee. Would you get on it, or wait for space on the dependable, newer model?
Herein lies the dilemma of the Oxford/AstraZeneca vaccine. It now seems likely that regulators will only approve a two-dose regime, with an efficacy rate of around 62 per cent, far less than the 95 per cent promised by Pfizer and Moderna.
Experts have already warned this could leave large proportions of the population vaccinated, but unprotected.
Yet compared to the US jabs, our home grown version will be far cheaper and much easier to roll out, meaning more people could get it more quickly.
So is it better for more people to have some protection, or should they wait for a better vaccine?
This is the headache that the Government will be faced with if the Medicines and Healthcare products Regulatory Agency (MHRA) approves the Oxford jab in the coming weeks as expected.
It is a puzzle that has divided scientists, with some believing it is not safe to give the Oxford vaccine to the most vulnerable people. Oxford has published preliminary results showing it can reach 90 per cent efficacy with a low-dose regime, but those are currently unsubstantiated.
“I think we can expect to hear criticism that the Government is trying to immunise the population on the cheap, given the lower cost and fewer logistical problems of the Oxford/AstraZeneca jab,” said Dr Simon Clarke, Associate Professor in Cellular Microbiology, at the University of Reading.
“We should remember that the Vaccines Taskforce has ordered enough of the Pfizer and Moderna jabs to immunise millions of people, and I think it would be better if higher risk groups received these vaccines, at least until Oxford’s half-dose/full-dose observation can be confirmed by further research.”
Paul Hunter, Professor in Medicine at the University of East Anglia, is also concerned that the confidence intervals for the Oxford jab mean the actual efficacy could be anywhere between 80 and 40 per cent. It may be too much of a gamble for the most vulnerable, he believes.
“You’ve got to give Oxford credit,” he said. “If it was all that we had there would be no argument. And if it was the only game in town then we would be leaping at it.
“Six months ago we would have jumped at an efficacy rate of about 60 per cent, but now there are alternatives.
“For me if I could have a 60 percent effective vaccine today or wait a month, I’d wait a month. But if I had to wait a year, then I’d have the Oxford vaccine.”
Developing a vaccine is not easy, and a 62 per cent efficacy rate is still a good result, particularly in just 10 months. Other companies have fallen by the wayside. This week the University of Queensland was forced to abandon its vaccine attempt after trial participants recorded false HIV positive results.
Drug companies Sanofi and GSK also announced a delay in their Covid-19 vaccine programme on Friday, after trials showed an 'insufficient response' in the over-50s.
Some researchers believe the Oxford jab may actually perform better than the 62 per cent efficacy rate suggests. Nobody in the vaccine arm became seriously ill or needed hospital treatment.
Mark Woolhouse, Professor of Infectious Disease Epidemiology at the University of Edinburgh, said: “I don’t think we should get too hung up on the numbers.
“My understanding is that in none of the trials anybody in the vaccine arm went to the hospital arm and died. That's a lot more than 62 per cent, so that's a 100 per cent benefit, but the problem is the numbers were small and the trials were not designed to answer the question how good these vaccines are at keeping people out of hospital and dying.”
The Oxford trial did show that 90 percent efficacy was achieved in a small part of the trial where participants were accidentally given a half dose in for their first injection, followed by a full dose several weeks later.
But the numbers were small and researchers said they could not substantiate the result. The half-dose arm also did not include enough older people for it to be licensed for the most vulnerable, so is unlikely to be approved in the elderly, if at all.
Several experts believe it could be a risk giving very vulnerable people a less effective vaccine, but that it ultimately may come down to availability, and ease of roll-out.
Dr Julian Tang, Clinical Virologist at the University of Leicester, said: “One might argue that 50-60 per cent protection might be better than none.
“But will there be a risk in terms of the behaviour of those vaccinated who may not actually be protected, as they behave more freely and expose themselves more to others, thinking they are protected?
“From the interviews that I’ve heard from those who have received the vaccine already - almost certainly yes - as they see the vaccine as a way to get their freedom back.
“The problem with this at the moment is that the virus is still very widespread in the community - so the chances of exposure are high.”
Professor Jonathan Ball, Professor of Molecular Virology, at the University of Nottingham, added: “In an ideal world we would have sufficient stock of the best performing vaccine to roll-out to the most vulnerable groups, but that might not be possible if supplies are limited,” he said.
“At the end of the day, even 60 or 70 per cent effectiveness is better than no vaccine at all.”