You have sent us a message ensuring that The Lancet journal has published a study which confirms that the “efficacy of the vaccine” is not “95%”, but between 0.84% and 1.3%, depending on the brand. This is MISLEADING: neither The Lancet journal has published a study about such a thing (it is about a comment signed by a group of scientists), nor is it true that in the document the data about the efficacy of the vaccines is questioned. What the document states is a datum about a different way to calculate the efficacy of the vaccines that is not static, but it varies as a function of the epidemiological situation in which the immunised person is found.
"The study of the prestigious scientific journal “The Lancet'' with peer-to-peer review confirms that the efficacy of the vaccine is not 95%, as the vaccines companies affirm, but this way: AstraZeneca 1.3%, Moderna 1.2%, J&J 1.2%, Pfizer 0.84%. They misled everyone by reporting relative risk reduction (RRR) instead of absolute risk reduction (ARR)"
The message states that the Lancet study indicates that the efficacy of the vaccines “is not 95%, according to what companies affirm”, but 1.3% for AstraZeneca, 1.2% for Moderna and J&J, and 0.84% for Pfizer. Both the official numbers and those quoted in the commentary are correct and complementary. The 95% efficacy corresponds, effectively, to the numbers that the authorities have been making public about the distinct vaccines. This way of measuring the efficacy is called relative reduction risk (RRR) and is correct, but there is another way of understanding the efficacy of the vaccine, and it is through the reduction of the absolute risk (ARR), which, instead of taking into account only the individual, as is the case with RRR, also considers the population as a whole. "The RRR should be analysed in comparison with the risk of being infected and contracting covid-19, which varies across populations and over time," says the Lancet paper. This combination of vaccine efficacy and epidemiological situation gives the ARR.
“We are not saying that vaccines do not work. We say they work, and we add considerations about the intrinsic efficacy of vaccines and their effectiveness in different populations”, Piero Olliaro, a researcher at the Centre for Tropical Medicine and Global Health at the University of Oxford (UK) and the lead author of the commentary, tells Verificat that it is not a "peer-reviewed" study, but the opinion of three experts. Therefore, pharmaceutical companies are "not fooling everyone", as claimed in the hoax.
Two ways of measuring efficacy
The RRR is a percentage that indicates the extent to which the injection is able to “prevent disease in those who suffer the risk of becoming infected and ill”, that is, developing severe cases of covid. On its part, the ARR has to do with the number of people who have to be vaccinated in order for an injection to be epidemiologically effective.
Thus, an RRR of 95% is focusing on those people who have already been immunised with a given vaccine, while an ARR of 1.2%, for instance, considers all individuals in a population and translates into the number of people needed to be vaccinated within a population at a given risk at a specific time. "For any given RRR, the ARR is higher when covid-19 case rates are higher, and decreases as they decrease," he explains.
With this article, the researcher does not pretend delegitimise the information provided by manufacturers on vaccines, but tries to explain that the political decisions that are taken in public health should not obey only to the RRR percentage: “Two vaccines with a very similar high efficacy (RRR 95%) can have a different efficacy depending again of the risk of covid-19”, he concludes.
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