However you feel about Mondays, it cannot be denied that the past three have been an exciting time for the world of immunology. On Monday 23rd November, for the third Monday in a row, we received news of another promising anti-COVID-19 vaccine trial. This time it was Oxford University and the British-Swedish pharmaceutical company AstraZeneca hailing the good news. The press release announced that their vaccine was 70% effective against COVID-19, drawing from Phase 2 and 3 trials in Britain and Brazil.
This is an impressive figure. However, it comes after the Pfizer-BioNTech and Moderna vaccines announced that their vaccines were both over 90% effective. As such, the announcement felt somewhat disappointing. This is despite the fact that the WHO has set a threshold of 50% efficacy for the development of a novel coronavirus vaccine. It may be the case that the world would have been more excited about these results had they not followed announcements from their more successful American rivals. Professor John Moore of the Weill Cornell Medicine College in New York agrees, saying “The trouble is that the Oxford-AstraZeneca vaccine received a lot of publicity over the summer and expectations were high… These expectations have not been met and now there is a pushback”.
But it seems that there may be more disappointment and confusion about the data than it first seemed. The Oxford vaccine trial recruited 23 000 volunteers from Brazil and the UK. Half of these brave volunteers received the vaccine and half received a placebo (something like a saltwater injection). Of those administered the jab, none were admitted to hospital with COVID-19, and none suffered a severe case. There were not any serious adverse reactions recorded either. These joint trials produced the 70% efficacy statistic that headlined last Monday’s press release. This is good news, but it has since emerged that there were mistakes made in the protocol.
The protocol stated that those receiving the jab would receive it in two doses, as is common with many vaccines. We now know that a third-party contractor made an error in the British arm of the trial. A subgroup of 3000 people received a full first jab, but only a half dose of the second jab. This produced a startling 90% efficacy against COVID-19. While this sounds simultaneously counterintuitive and promising, the subgroup was very small compared to the entire trial population. Statisticians were forced to use subgroup analysis on this group, which can increase the likelihood of false positives. Furthermore, the subgroup consisted of only healthy under-55-year-olds, so the 90% efficacy figure may not hold for the entire population.
Oxford produced their 70% efficacy number by averaging their 90% effective subgroup and their 62% effective group in Brazil. Suddenly 62% seems even less impressive. That is not the end of the confusion, either. While the competing two vaccines used only Phase 3 trial data in their reports, Oxford used Phase 3 trials from Brazil and combined Phase 2 and 3 trials from the UK. The trials also used different placebos. And there is a story emerging of a man in Brazil claiming to have suffered serious adverse reactions to the vaccine.
We mustn’t be too harsh on Oxford and AstraZeneca, though. For starters, where Pfizer and Moderna only counted symptomatic cases of COVID-19, Oxford counted asymptomatic cases as well. This may account for part of the gap between the 90% and 70% efficacy ratings. More importantly, the Oxford vaccine has some serious advantages to the other jabs. One notable selling point is price: the Oxford-AstraZeneca vaccine costs approximately £4 per dose, compared to £15 for Pfizer-BioNTech and £28 for Moderna. Multiply those differences across the entire UK population and you can see why the Oxford vaccine seems favourable. It is also far more practical to produce and distribute. The Pfizer vaccine needs to be stored at -70˚C most of the time and only keeps in a regular fridge for a few days. Oxford’s vaccine can be stored up to 6 months in a normal fridge.
In the end, the data we have from Oxford is both promising and worrying. Perhaps there were marketing executives in board room meetings urging the scientists to release data before it had been thoroughly looked over. Was this a money-grabbing move? AstraZeneca has promised not to make a profit from this vaccine during the pandemic, but we may never know the executive’s intentions. It is my personal opinion that Oxford and AstraZeneca made a mistake in releasing these figures as quickly as they did. However, I have a lot of faith in this vaccine. It’s cheaper production and distribution makes it ideal for developing countries.
Before this pandemic, scientists had never created a successful coronavirus vaccine (there are no vaccines against SARS or MERS). Now, in the span of three weeks, we have three promising vaccines – with more on the horizon. While there are still unanswered questions about the Oxford vaccine, it cannot be denied that the scientific community has performed an incredible feat that has changed the landscape of this pandemic as we know it.
