A classic head to head – Pfizer versus Oxford – efficacy. the two vaccines have not yet been tested head to head, so it’s impossible to say which is best.
But it is true, of course, that the Pfizer vaccine boasts an efficacy of 95 per cent, compared to something around the 70 per cent mark from Oxford. Immunity also appears to kick in a bit quicker with the Pfizer jab at 14 days, compared to 22 for Oxford’s shot.
In theory, at least, Pfizer’s RNA technology (although never used before in a mass vaccination programme) is also “cleaner” in the sense that the RNA code snippet it uses to deliver immunity vanishes from the body soon after doing its job. But such comparisons are largely academic. The trial data for both vaccines is robust but limited and the real numbers on efficacy will only emerge a few years down the line once tens of millions of doses have been administered. Much more important is that both vaccines, based on the trial data available, appear highly effective at protecting against severe disease. In all the trials run to date, no one vaccinated has been hospitalised or died of Covid-19. Experts are not yet certain if either prevent against transmission.
Both jabs also appear to be safe. Like many vaccines, they cause some short term discomfort in roughly one in 10 people and vomiting and fever in about one in 100. But more serious vaccine-specific adverse effects have not been reported. It remains possible issues may emerge in the months to come but tens of thousands of people have now been given the Oxford vaccine with no ill effects and millions have received the Pfizer immunisation. “The MHRA will have carefully scrutinised the evidence on this Covid-19 vaccine to ensure that it is both safe and effective,” said Prof Arne Akbar, president of the British Society for Immunology. “Although development of this vaccine has occurred quickly, all the same rigorous safety standards and checks have still been carried out.” The most obvious and certain differences between the two jabs are practical ones concerning logistics and cost. Just as with cars, different vaccines are better suited to some tasks than others, and on this measure the Oxford shot shines bright – a Fiat Punto, compared to Pfizer’s Porsche. While the Pfizer jab must be “deep frozen” and used within five days of leaving the dry-ice containers it is shipped in, the Oxford jab can be kept in a fridge, between 2 and 8C for up to six months. This will be a huge relief to those orchestrating the biggest vaccination effort in history, both in Britain and overseas. “We have concerns over the logistical challenges the Pfizer vaccine has left us with. It’s been hugely difficult to manage – the deep freeze conditions, the rapid timeframe it needs to be used in,” said Dr Richard Vautrey, chair of the BMA’s GPs’ committee. “It’s been a mammoth task for practices… We hope the AstraZeneca vaccine will remove many of these problems because it can be stored in a standard fridge and there are going to be more doses available.” And then there are the costs. The UK government won’t say what it is paying for the Pfizer vaccine, citing commercial confidentiality, but leaked figures show the EU is paying over £10 per dose. The Oxford shot, in contrast, comes in at around £1.60 and the company has pledged to continue to provide it at cost until the summer. In low and middle-income countries, it will continue to be sold at cost in perpetuity – perhaps the single best prospect of bringing the pandemic to an end globally. Dr Richard Hatchett, CEO of CEPI, said: “The Oxford-AstraZeneca Covid-19 vaccine is extremely attractive in that it is inexpensive, scalable, and can be stored at 2-8 degrees Celsius. “These attributes will enable its use worldwide, including in low-income and middle-income countries, alongside other safe and effective Covid-19 vaccines, and the large supplies that will become available in 2021 mean that this vaccine could be a gamechanger in terms of our efforts to end the acute phase of the pandemic.” And what of mutations? It’s unlikely the new variant of the virus it will have much, if any, impact on either vaccine and we will only find out as the jabs are administered, say experts. Over time – a year or more – all Covid vaccines may need to be tweaked like the annual flu jab to keep up with “viral drift”, they add.