Third to arrive on the market, the AstraZeneca vaccine for Covid-19 has never enjoyed the same appreciation as the “rivals” Pfizer-BioNTech and Moderna. A meaningless comparison, however, since all three vaccines available today are proving to be equally effective in reducing the chances of developing severe forms of Covid-19 that require hospitalization. A scientifically unjustified mistrust but born from a series of fortuitous “errors” in the first clinical trial, continued by a back and forth decision on which population groups should have received this vaccine and, finally, by a communication that is not always clear. Which has had devastating effects, with entire sections of populations wary and who have preferred not to be vaccinated while waiting for a better product.
AstraZeneca, how many doubts about the vaccine
by Elvira Naselli
All vaccines currently on the market and testing for Covid-19 have the objective of stimulating the immune system to produce antibodies capable of recognizing and eliminating Sars-Cov-2. But unlike the disease, where the virus in its entirety provokes an immune response, the vaccines made in recent months stimulate the production of antibodies against the Spike protein, the surface protein that the virus uses to interact with the ACE-2 receptors and penetrate inside the cell to be infected. There are different ways to produce a response against “Spike”. Essentially, the vaccines currently approved belong to two categories: those with mRNA (Pfizer-BioNTech and Moderna) and those with a viral vector (AstraZeneca).
While in the past the most common method used to create a vaccine was to use inactivated or attenuated viruses, today the particularity of both approaches is to provide the cell with the information necessary to “self-produce” a portion of the Spike protein. In the vaccines of Pfizer-BioNTech and Moderna the information is contained in the mRNA, in that of AstraZeneca a virus harmless to humans is used which acts as a “transporter” of a portion of DNA that is needed by the cell to produce part of the protein Spike. The result is the same: when the protein is produced and released outside the cell, the immune system recognizes it as foreign and starts the production of antibodies.
Covid: vaccines compared. The cards
edited by Cinzia Lucchelli
Approved in Europe for the third time in late January by Ema, the European drug agency, the safety of the AstraZeneca vaccine has never been questioned. What slowed down approval and led to skepticism was the case of the “halved doses” during the trial. For technical reasons (the use of a different method of dosing the viral particles) an error occurred that led a small number of vaccinated people to receive half a dose for the first injection and a full dose for the second. An error that initially led to a lack of data on efficacy in the over 55 population. Nevertheless, by virtue of the good results obtained in the different age groups with the correct doses, Ema on 29 January approved the vaccine from 18 years of age without no age limit. An indication initially not fully implemented by Aifa, the Italian drug agency, which first approved the vaccine from 18 to 55 years and then extended it shortly after up to 65 years.
Covid, three-month interval between doses and the Astra vaccine becomes more effective
But be careful to think that this is a gamble. The data supporting the goodness of AstraZeneca’s vaccine in protecting the population from Covid-19 are becoming increasingly solid. The effectiveness in avoiding new cases was around 60% in the trials that led to approval, but the data does not give a good idea of the impact of vaccination on the health system. To understand this, the case of Scotland is emblematic. Analyzing the data relating to the administration of 1.14 million first doses, the extraordinary effectiveness of vaccines in preventing new hospitalizations due to the disease emerged: the Pfizer-BioNTech vaccine reduced them by 85%, AstraZeneca by 94% 5 weeks after first dose. Important results also obtained in the later age groups where the drop in hospitalizations was 81%.
Not only that, a recent study published on The Lancet showed that a single dose ensures constant protection in 76% of cases over a period of between three weeks and three months. Going further, with the second dose, the percentage rises to 82%. A figure, that relating to the effectiveness that increases if the second administration takes place three months later, is the basis of the decision of many nations to recommend the “recall” no earlier than two months.
Covid vaccines: the mess of doses
by Antonio Cassone
Important results, those that are emerging where administrations take place at a sustained pace on a large scale, which have led in these hours to Aifa’s decision to extend the use of the vaccine even beyond the age of 65. Vaccine that in the second quarter of the year will be available in 20 million doses. This is excellent news if we consider the current situation of full third wave where the main problem is the umpteenth overload of the hospitals. All vaccines approved today have shown that they can lighten this burden by drastically reducing the percentage of people requiring hospitalization. The real challenge today is therefore to speed up the vaccination campaign: for AstraZeneca, out of one and a half million doses delivered in the last month, only 375,000 were administered.
