One of the main vaccines against Covid-19, the one developed by AstraZeneca and the University of Oxford, has come under fire since the publication of figures on its effectiveness. A trial that seems unfair, according to several scientists interviewed by France 24.
He has long been the star of candidate vaccines against Covid-19. Developed by Oxford University in partnership with pharmaceutical giant AstraZeneca, ChAdOx1 nCoV-19 was the first to gain media attention, and the first to enter human trials. And Monday, November 23, AstraZeneca claimed that it had about 70% effectiveness in protecting against Sars-CoV-2.
But since then, this vaccine has found its way into the dock. The published data has been criticized, and “confidence” in Astrazeneca’s scientific approach “suffered”, summarizes the New York Times. Among the three groups in the race to be the first to put a vaccine on the market, AstraZeneca is the only one whose stock market value has fallen, underlines the Financial Times. The other two, Moderna and Pfizer, saw their share price increase by more than 10% after announcing that their vaccine was more than 90% effective.
The problems for the ChAdOx1 nCov-19 started when the media took a closer look at the numbers. The 70% effectiveness announced represented, in reality, an average obtained from the results of different series of injections made with different dosages. The vaccine was in fact only 62% effective when the patient received a twice dose, but was shown to be 90% effective when a person received a first injection of only half a dose.
Confusing results which seem to indicate that the vaccine would protect better when less injected. Oxford scientists working on ChAdOx1 nCoV-19 admitted that they could not explain this phenomenon. Asked by various media, AstraZeneca also admitted that there had been a human “error” in the dosage of the vaccine for the trials which resulted in the result of 90% effectiveness.
This is not the kind of confession we want to hear about tests as important as those conducted on a vaccine against a virus responsible for the worst pandemic in more than a hundred years. From there, all of AstraZeneca’s claims were taken with a grain of salt.
Pressed for questions, the laboratory then admitted that all the volunteers who took part in the trial, which demonstrated an effectiveness of 90%, were under 55 years old. “The fact that this dosage has not been tested on older people, particularly vulnerable to Covid-19, could pose a problem in receiving emergency marketing authorization from the authorities,” notes the New York Times.
>> To read also on France 24: “Vaccine against the Covid-19: what will be of poor countries?”
The data published by the laboratory do not concern, moreover, “not a single large test as was the case for Pfizer or Moderna”, underlines the Wired site. AstraZeneca “combined the results of two trials, one conducted in the UK, the other in Brazil, even though they showed differences in the way these tests were conducted,” the site continues.
“I don’t see anything worrying about it”
What discredit the AstraZeneca vaccine? This would be very bad news for the fight against the pandemic, especially in low-income countries. ChAdOx1 nCov-19 is indeed based on a less expensive technology than that used by Moderna or Pfizer and the doses could be sold for much less. Unlike the other two vaccines, the Oxford vaccine also does not need to be stored at very low temperatures, which logistically means that it would be easier to deploy quickly and on a large scale.
According to scientists interviewed by France 24, criticism against AstraZeneca’s announcements should not be seen as calling into question the vaccine. “I don’t see anything worrisome here. These are intermediate results from tests on a few participants. These numbers will change quickly when we have more data, which will allow us to have a better understanding of the effectiveness of all these vaccines, “says Zania Stamataki, an immunologist at the University of Birmingham who works on neutralizing Covid-19.
Same analysis for Morgane Bomsel, virologist and research director at CNRS and at the Cochin Institute. “We do not yet have enough hindsight to draw conclusions. It has only been two weeks since these results were published, and they are only press releases,” she said.
None of the teams working on these vaccines has, in fact, yet published the details of their results in a scientific journal. It would therefore be urgent to wait before criticizing a particular vaccine candidate. “Scientifically, the only thing that can be said at the moment is that the three vaccines are showing encouraging signs of effectiveness in protecting against Covid-19,” says Zania Stamataki.
Indeed, even if the Oxford vaccine was only 62% effective, it would already be very promising. “We must not forget that the vaccines against the seasonal flu reduce the risk of being infected by only 40% to 60%”, underlines the researcher from the University of Birmingham.
The “mistake” in the dosage that led to the avalanche of criticism of the results published by AstraZeneca could also be a blessing. Scientists may have unwittingly found the ideal dosage. The fact that by injecting less vaccine elicits a better immune response against the virus can indeed be explained. One of the possible reasons is the way vaccines like the one from Oxford work: “You inject a Sars-CoV-2 protein with an adjuvant. [en l’occurrence un virus ayant des effets bénins sur l’homme, NDLR] which tells the immune system to defend itself. But if we put too much adjuvant, the body risks focusing on it and ignoring the Sars-CoV-2 protein “, summarizes Morgane Bomsel.
For her, as for Zania Stamataki, the real test for the three vaccines does not lie in figures that are not yet final. There are two essential questions for which there is, as yet, no answer: how long does the protection provided by these vaccines last, and how effective are they for the populations most at risk?
Perhaps the real error stems from the decision of all these labs to publish intermediate results. “This is something that we do regularly in science, but generally the media are not interested in it, so researchers are not used to having to explain that we should not draw too many conclusions, ”notes Zania Stamataki.
But she thinks, despite everything, that it was necessary: ”We ask people to make so many sacrifices to protect themselves against this virus that it was important to tell them, with supporting figures, that there is a real hope and that vaccines which have demonstrated efficacy were developed in less than a year. “