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In addition to the Pfizer, Moderna, and Johnson & Johnson vaccines currently approved in the US, several other vaccines are used in other countries. One of them, the Oxford / AstraZeneca vaccine, has not yet been approved in the US and has been the subject of controversy. Here is an overview of what we know.
How is this vaccine different from the others we have?
The Oxford / AstraZeneca vaccine uses an adenovirus (related to one of the viruses that cause the common cold) to carry a piece of DNA that encodes instructions for the coronavirus spike protein. Our cells use this DNA to make the protein, and then our immune system recognizes the protein as an invader and makes antibodies that can recognize and fight the virus. This is a similar mechanism to the Johnson & Johnson vaccine. In contrast, Pfizer and Moderna vaccines use mRNA in a lipid bubble instead of DNA in a modified virus.
The AstraZeneca vaccine is given in two doses and can be stored at refrigerator temperature for six months. It is also supposedly cheaper than the other vaccines about $ 4 per dose instead of $ 10 for Johnson & Johnson or $ 20 or more for the mRNA vaccines.
Where is this vaccine already being used?
According to the New York Times vaccine trackerIt is approved for emergencies in 46 countries as well as the European Union and is fully approved in Brazil. The UK, Australia, India, Canada and Mexico are among the countries where it is currently used.
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Why is it not approved in the USA?
The first large-scale trials of the vaccine, which were completed in December 2020, set the stage for several countries to approve the vaccine and begin using it. There were concerns at the time that studies were being conducted differently in different countries with different time intervals between doses, and that some participants were given the wrong dose (although it turned out to be well protected from COVID despite the mistake).
The company conducted a recent study that included participants in the United States announced results of that study this week. They plan to apply to the FDA for emergency approval so that this vaccine can also be used in the United States.
Haven’t other countries stopped using it?
Earlier this month, several countries stopped using the AstraZeneca vaccine because some people who received the vaccine reportedly developed blood clots. (Blood clots can have a variety of causes and occur as a result of COVID.) However, an analysis found that the occurrence of blood clots was no more common in people who received the vaccine than in a similarly large group of people. In other words, there was no reason to believe that the vaccine was causing the clots. The vaccination programs were resumed.
Is it as good as the other vaccines?
Like the other vaccines currently approved in the US, it appears to provide 100% protection against life-threatening cases of COVID, with less effectiveness against mild and moderate cases of the disease. The full data has not yet been released, but the total numbers are comparable to the other vaccines we have.
Somewhat worrying is that the numbers used in AstraZeneca’s press release were out of date at the time of its publication, and it appears that The company chose a 79% effectiveness figure from a previous analysis instead of the 76% calculated using the latest data. Vaccine trials have an independent data security monitoring body that alerted the discrepancy. However, this change in numbers does not mean that the vaccine is necessarily less effective, it just undermines the experts’ trust in the company doing the trials. We will learn more in a few weeks, when the FDA is expected to publish an informational document summarizing and interpreting the data from the US study.