A study in pre-publication conducted at the University of Trento, in Italy, agitates the anti-vaccine spheres in the United States. The article is used as a source to discredit Covid vaccines saying that the booster dose is only 20% effective. It is a truncated and reduced interpretation of the work of Italian researchers. What should we remember then?
Comb through the scientific literature
The objective of the study is to look into the progressive reduction of theimmunity vaccination against several variants of the coronavirus, of which Omicron (B.1.1.529). For this, the researchers did not recruit volunteers and did not follow them for several months by testing their rate ofantibody vaccinations at regular intervals; they carried out a bibliographical synthesis of the studies providing evidence of the decline in the effectiveness of vaccines over time and re-analyze all the results obtained. The selection of studies is done according to strict criteria. Of the more than 500 pre-selected studies, only 12 were ultimately included in the final analysis – all being case-control, retrospective or prospective studies that estimated the effectiveness of an anti-Covid vaccine in comparison with a group witness. The vaccines considered are those of Pfizer, Moderna and Astra Zenecaand efficacy against symptomatic forms and asymptomatic caused by the Alpha, Delta and Omicron.
For each of the 12 studies, the Italian scientists extracted the following data: the efficacy of two doses against confirmed cases of the Delta variant; the efficacy of two doses against symptomatic forms of Covid-19 due to the Delta and Omicron variant and the efficacy of two initial doses plus a booster dose against symptomatic and asymptomatic forms due to Omicron. So much for the framework of the research, but what about the results?
A 20% effectiveness of vaccines against Omicron?
This review work concludes that the cumulative efficacy against the Delta variant of the Pfizer and Moderna vaccine, 14 days after the second injection, is 92.4% and 94.7% respectively. For the AstraZeneca vaccine, the efficiencies calculated by the various studies are more heterogeneous, a Quebec study found an efficacy comparable to that of Pfizer and Moderna, while two others, a lower one around 80%. At three months post-vaccination, the effectiveness of AstraZeneca is 74% against 85.6% and 86.5% for Pfizer and Moderna respectively. At nine months post-vaccination, the three formulas show the same efficacy, approximately 70.8%. The same trend is observed for the Omicron variant, but for three doses of Pfizer: 82.4% after 14 days, 31.5% after 6 months and 19% after 9 months.
The efficacy of the vaccines, 14 days after the second dose, against the symptomatic forms of Covid-19 caused by the Delta variant is 93.6%, 96.2% and 76.2% for the Pfizer, Moderna and AstraZeneca vaccines respectively. It drops to 64.4%, 74.1% and 40.2% after six months for the Pfizer, Moderna and AstraZeneca vaccines. For Omicron, six months after the administration of the second dose of vaccine, the efficacy against the symptomatic forms of the disease is 8.3%, 7.5% and 12% with the formulations of Pfizer, AstraZeneca and Moderna respectively .
Be careful with preprints
At the end of this analysis, the authors note in the abstract of their article: A rapid decline in the effectiveness of booster against Omicron is observed, with less than 20% efficacy against 25% efficacy against symptomatic forms of the disease at nine months after injection of the booster “.
This is where the 20% efficacy put forward by the American anti-vaccines comes from. They present this figure as the overall effectiveness of the vaccine against Omicron whereas it is that calculated after nine months. The gradual disappearance of vaccine immunity to the coronavirus is a phenomenon observed by scientists since the start of the pandemic, but it is particularly marked by variants of the Omicron lineage. Many of the pre-published studies do not appear in peer-reviewed scientific journals or undergo extensive editing. This prompts us to remain cautious about the results presented here.
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