How the AstraZeneca vaccine works and how effective it is


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Currently, Spain is vaccinated against the coronavirus using the doses developed by Pfizer / BioNTech, Moderna and AstraZeneca /Oxford University. However, due to the little evidence on the effectiveness of the latter in patients over 55 years of age, the Ministry of Health announced that AstraZeneca vaccines will only be intended for adults under 55. For this reason, there are many who have doubts about this vaccine. What does it consist of? What are the differences between this and the other two? What is its reliability?

How the AstraZeneca vaccine works

The vaccine developed by researchers at the University of Oxford is of the type vector viral no replicante. These types of vaccines, as the Center for Disease Control and Prevention (CDC) explains, contain a manipulated viral version of another virus (the vector) that works by triggering a reaction in our cells by giving them instructions.

In this case, the AstraZeneca vaccine contains a type of virus, demoninated adenovirus, which is the cause of colds in chimpanzees. This, which does not affect humans, enters a cell of the body and uses the cellular machinery to produce a innocuous portion, that is, minimal, without effects, of the SARS-CoV-2 that causes the coronavirus. This portion is called the Spike protein and it is found on the surface of the virus that causes Covid-19 disease.

When the cell into which the adenovirus has been introduced produces the spike protein of the coronavirus, the immune system recognizes this new element as something foreign. This triggers a response and the immune system begins to create antibodies and to activate other immune cells to fight what it considers an infection.

In the end, the human body learns to recognize the coronavirus in possible future infections and to generate antibodies so that it does not develop and does not cause serious symptoms.

Differences with Pfizer and Moderna vaccines

Currently, the AstraZeneca and Oxford University vaccine is the only one distributed in Spain that works with a non-replicating viral vector. Both Pfizer and Moderna are of the type Messenger RNA (mRNA). These types of vaccines, as the CDC explains, teach our cells to produce a protein present on the surface of SARS-CoV-2 (as in the case of the British vaccine, this protein that is produced is the Spike protein) , which triggers an immune response within the body.

In these cases, therefore, the body’s cells are instructed directly to produce a protein that the immune system recognizes as foreign and triggers a answer to delete it.

On the other hand, these types of vaccines are more difficult to preserve and are somewhat more expensive. While AstraZeneca vaccine can be stored at temperatures of between 2º and 8º centigrade, Pfizer’s needs to be around 70 degrees below zero and Moderna’s needs to be about 20 degrees below zero.

As for the price, the Pfizer vaccine exceeds 15 euros per dose and Moderna’s reaches 21. On the other hand, Oxford’s is the most economical, since each dose barely reaches the three euros.

What is the reliability of the AstraZeneca vaccine

According to the World Health Organization, the AstraZeneca vaccine, whose technical name is AZD1222, has an effectiveness of 63,09 % against symptomatic coronavirus infection. However, it seems that a wider distance between doses increases the effectiveness of the same as well as the injection of lower doses. The latest studies announce an effectiveness of up to 90 %.

However, the vaccine trials have not shown high effectiveness in patients over 55 years of age and that is why many countries have decided to use these doses for the vaccination of the youngest.

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