A few days after the announcement of an effectiveness of 70 to 90% of its vaccine against Covid-19, AstraZeneca has just recognized that some of the participants in the clinical trial had only received a half-dose in first injection instead of a full dose. An error that will not facilitate adherence to vaccination campaigns that are being prepared around the world and in France.
- The AstraZaneca laboratory had announced an effectiveness of its vaccine of between 70 and 90%
- The explanation for this margin is an error in the dosage of the vaccines administered to the participants in the clinical trial.
A vaccine whose effectiveness is between 70 and 90% … The announcement on November 23 by the AstraZeneca laboratory of the results of its clinical trials on the candidate vaccine against Covid-19 reinforced a series of other good news . After Pfizer, Moderna and the Russian Sputnick, the British laboratory brought its share of optimism about an imminent victory, thanks to vaccines, against Covid-19.
In the general enthusiasm, the curious range of the level of effectiveness of the vaccine candidate developed by AstraZaneca with researchers from the University of Oxford seemed anecdotal. This variation of 70 to 90% in fact hid an incredible error committed during clinical trials, an error underlined and commented on on November 25 in the New York Times : of all the participants in this trial, 8,900 had indeed received two injections of full doses, but 2,800 other participants had only received half-doses in the first injection. “A problem with the way some of the vaccine doses were made,” according to the AstraZeneca spokeswoman.
Better results with half doses
But the surprises didn’t stop there. Because if this error came, finally, to explain the difference between the 70 and the 90% of effectiveness, the best results were obtained… by the group having received only half-doses in first injection! And to date, no explanation has been given for these astonishing results. Why such a difference in the effectiveness of the vaccine at different doses and why did the smallest dose give the best results? “We don’t know,” replied the researchers from AstraZeneca and Oxford…
On the other hand, for the defense of the laboratory, these incongruous figures are a godsend. “The reality is that this could end up being a pretty useful mistake,” Menelas Pangalos, the research executive, dared in an interview with The New York Times. Implied, why not rely on the 90% effectiveness in the “half-dose” group to define the right dosage… The laboratory has also declared that it is planning a new global trial “to compare the two regimens” .
Some within the scientific community show less leniency! “AstraZeneca and Oxford get a bad mark for transparency and rigor with regard to the results of the vaccine trials they have reported”, denounced on Twitter Natalie Dean, an expert in this field at the University of Florida. Especially since beyond this incredible error, the results announced by the laboratory are based on the pooling of the conclusions of two clinical trials designed differently in Great Britain and Brazil, a practice deemed “not standard” in the communication of results of drug or vaccine trials.
“A setback in the campaign to control Covid-19”
Following the recognition of the dosage error by the laboratory, Stephanie Caccomo, spokesperson for the FDA, the American authority in charge of marketing authorizations, refused to say whether it would harm the chances of the AstraZeneca-Oxford vaccine being licensed. On the other hand, as several experts in the NYT point out, this case is indeed “an unexpected setback in the global campaign to control the devastating pandemic”.
While in France, the green light from the health authorities is expected to launch, possibly at the end of this year, a vaccination campaign against Covid-19, AstraZeneca’s error risks reinforcing a mistrust that is already rises to 46% of the population against vaccines.
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