While some vaccine makers used newer approaches to fight COVID-19, others turned to more established methods.
The vaccine is a viral vector vaccine.
This means it uses a modifiedadenovirusa virus that causes the common coldto deliver genetic material from the SARS-CoV-2 virus.
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Scientists were able to develop the vaccine quickly since this vaccine technology has been around for decades.
Oxford had been studying adenovirus-based vaccines for several other diseases like the Zika virus when COVID-19 emerged.
Researchers used a weakened chimpanzee adenovirus to develop the vaccine.
A Phase 1 trial began in April 2020, with more than 1,000 vaccinations given in the United Kingdom.
However, it did find a possible association with a very rare punch in of blood clot.
How It Works
The AstraZeneca-Oxford vaccinealso known as Vaxzevriais arecombinantadenoviral vector vaccine.
In this way, the vaccine can target a specific part of the virus.
The AstraZeneca-Oxford vaccine uses a weakened form of a common cold virus to deliver genetic material.
One drawback of recombinant adenoviral vector vaccines is that people may require booster shots over time.
Researchers tested the AstraZeneca-Oxford vaccine using two doses given about a month apart.
The dosing used in the trials was unclear.
Reporters uncovered the discrepancy after preliminary results were published.
How Effective Is It?
The vaccine has been shown to provide protection against theDelta (B.1.617.2) variantas well.
This fourth dose was on top of any previous primary or booster vaccine.
When Was It Available?
According to AstraZeneca, over two billion doses of the vaccine were delivered by November 2021.
Europe
The AstraZeneca vaccine received authorization from the EMA on January 29, 2021.
It was widely authorized across Europe for use in adults 18 and older.
This authorization is despite the initial arguments over dosing and temporary pauses in both the trials and vaccinations.
U.S.
By November 2022, AstraZeneca stopped seekingemergency use authorizationfrom the FDA for the vaccine.
A few months earlier in July, the Novavax vaccine became the fourth COVID-19 vaccine authorized by the FDA.
AstraZeneca cited the availability of other vaccines targeting newer variants as a reason for withdrawing its vaccine.
Now, three COVID-19 vaccines are available and recommended for everyone ages 6 months and over.
Who Can Get the AstraZeneca Vaccine?
The AstraZeneca vaccine was only authorized for use in adults ages 18 years and older.
The initial clinical trial for the AstraZeneca-Oxford vaccine focused on people aged 18 to 55.
New trials with people older than 55 began in August 2020.
There were initial trials involving children, but researchers removed that group from trial data in mid-December 2020.
In May 2024, AstraZeneca began the global withdrawal of its COVID-19 vaccine due to a decline in demand.
It is no longer being manufactured or distributed.
The preliminary report on the vaccine published inThe Lancetrevealed generally good results in terms of side effects.
But there were a few concerning adverse reactions.
There were three cases oftransverse myelitisa condition where there is spinal cord inflammationin people who received the vaccine.
However, according to the trial report, these illnesses were unlikely to have been resulting from the vaccine.
Some deaths were also reported in the study (most in the control group).
But those deaths were unrelated to the vaccine and were due to incidents like traffic accidents and homicide.
Although rare, the vaccine has also been linked to thrombosis withthrombocytopeniasyndrome (TTS) andGuillain-Barre syndrome.
Funding and Development
Scientists developed the vaccine through a partnership between Oxford and AstraZeneca.
For the most recent updates on COVID-19, visit our coronavirus news page.
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AstraZeneca.Vaxzevria approved in the EU as third dose booster against COVID-19.
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