After the European Union and the European Medicines Agency (EMA), HAS gave the green light on February 2 to the Swedish-British AstraZeneca/Oxford vaccine. In France, the vaccine against Covid-19 is recommended for two priority populations: health and medico-social professionals and 50-65 year olds.
AstraZeneca: a recombinant adenovirus vaccine
First thing to know : unlike the Pfizer/BioNtech and Moderna vaccines (which are messenger RNA vaccines), the AstraZeneca vaccine against Covid-19 is a recombinant adenovirus vaccine.
What does it mean ? “To compose this recombinant vaccine, a monkey virus (an adenovirus) has been genetically modified to integrate a small part of the virus against which one wishes to develop immunity.“explains Dr. Steve Pascolo, an immunologist at the University of Zurich.
In this case, as part of the AstraZeneca/Oxford vaccine, the famous S protein was added to the (previously attenuated) monkey virus which allows the coronavirus Sars-Cov-2 to enter our cells – in the manner of a key. It is this famous “key” which, after vaccination, serves as a “recognition marker” for the immune system: it then produces antibodies specifically directed against Sars-Cov-2.
AstraZeneca vaccine against Covid-19: is it as effective as the others?
According to Dr. Steve Pascolo, the AstraZeneca vaccine against Covid-19 could prove less effective than messenger RNA vaccines (Pfizer/BioNtech, Moderna and possibly CureVac within a few weeks).
Why ? It has been said: “recombinant vaccines consist of two elements: an attenuated monkey virus (adenovirus) and a “piece” of the virus against which one wishes to protect oneselfrecalls Dr. Pascolo. The immune system, for its part, sees two “threats” arriving: it therefore begins to build defenses against the target virus (here, Sars-Cov-2) but also… against the monkey adenovirus!“
In short: the attention of the body’s defense system is divided in two, “which can potentially result in incomplete immunity“. So by less efficiency.
AstraZeneca vaccine: it is about 60% effective. Of course, you have to put things into perspective. If messenger RNA vaccines show an efficiency of more than 90%, the Swedish-British vaccine AstraZeneca “still” reaches 60% efficiency according to the report of the European Medicines Agency (EMA). This is the average effectiveness of our flu vaccine!
AstraZeneca vaccine: how effective in people aged 65 and over?
This is “the” question we are asking ourselves at the moment: does the AstraZeneca/Oxford vaccine work in adults over 65?
The controversy arose in Germany: this Thursday, January 28, 2021, the German vaccination commission (STIKO) thus limited the indications for the British vaccine to adults aged 18 to 64 because “the data currently available are insufficient to assess the efficacy of vaccines beyond the age of 65“. On February 2, 2021, the High Authority for Health followed the German example: the AstraZeneca vaccine is only recommended before the age of 65.
For its part, the AstraZeneca laboratory defends itself: “the latest analyzes (…) support the hypothesis of vaccine efficacy in the over 65 age group“said the spokesperson for the group, at the end of January 2021.
AstraZeneca Covid-19 vaccine: is it safe?
The response of Dr. Steve Pascolo, immunologist: “in 1998, I started developing messenger RNA vaccines with a view to safety. Messenger RNA is a minimal vector that encodes only one protein. In addition, it is quickly degraded and leaves no traces in the body. Conversely, adenoviruses are DNA vectors: this genetically modified DNA (combining elements which, in Nature, would never have met) penetrates the nuclei of cells. There is therefore a potential risk of integration into our genome, which does not exist in the context of mRNA vaccines which cannot modify our genes in any way..”
“Of course, the AstraZeneca vaccine has passed the validation stages (safety and efficacy). However, I am a bit worried and I fear the occurrence of short, medium or long term problems with the AstraZeneca or Johnson&Johnson adenovirus vaccines.” In a press release published on February 2, 2021the High Authority for Health (HAS) estimated that “efficacy and tolerance“AstraZeneca vaccine”are satisfactory“.
Thanks to Dr. Steve Pascolo, immunologist at the University of Zurich (Switzerland), interview February 2021.
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