Analysis of published data on AstraZeneca AZD1222 vaccine to prevent Covid-19

The AstraZeneca AZD1222 vaccine against Covid-19 is the third to be granted conditional marketing authorization in Europe. This decision by the regulators is based on data from a study published in The Lancet which presented the results of an interim analysis of 4 very heterogeneous randomized trials. This analysis shows that this vaccine reduces the relative risk of developing symptomatic, mostly benign Covid-19 by 62.1 % (CI95 = 41.0-75.7) with the two doses provided in the protocol and by 90.0 % (CI95 = 67.4-97.0) when the first dose was half of that expected (subgroup and post-hoc analysis = exploratory result to be confirmed). These reductions should be put into perspective with a risk of between 1.56 % and 1.62 % observed in control subjects. These results do not mean that 62.1% or 90.0% of vaccinated subjects are protected. There is no conclusive evidence in people aged >= 65 years on the spread of the virus, nor on the duration of immunity and protection. The effects of AZD1222 in intensive care use, severe forms, specific or total mortality have not been evaluated. Tolerance was generally satisfactory and similar to that observed in the control groups of serious adverse reactions or of concern. Although this complex publication contains numerous methodological and biostatistical biases leading to a level of evidence that is far from optimal, it is plausible to consider that this vaccine has a favorable efficacy/adverse events ratio pending the publication of the final results. This article offers an in-depth, critical and commented analysis, based on the available data on the benefits and risks of this third vaccine.