The vaccine made in the UK is less expensive than Pfizer-BioNTech and Moderna products, and can be stored at refrigerator temperature.
The Oxford-AstraZeneca COVID-19 vaccine was created by the University of Oxford and its Anglo-Swedish pharmaceutical partner, AstraZeneca.
Independent scientists have confirmed that the vaccine is “safe and effective” in preventing symptomatic COVID-19, according to preliminary results from its phase three trials published in The Lancet in early December.
Phase three is a large trial involving thousands of people, to prove that the vaccine protects people.
The vaccine made in the UK is important because it is cheaper than the other two main vaccines produced by Pfizer-BioNTech and Moderna.
Unlike its main competitors, it can be stored at a regular refrigerator temperature.
With the availability of more established Oxford technology, the vaccine is also easier to mass-produce and AstraZeneca has vowed not to take advantage of it during the pandemic.
Pfizer-BioNTech’s product costs around £ 15 per dose ($ 20), Moderna’s is around £ 25 ($ 33) and the Oxford-AstraZeneca vaccine is available at a much cheaper price of around £ 3 ( $ 4).
The vaccine can be stored, transported and handled for at least six months at 2-8 degrees Celsius (35-46F).
Pfizer and Moderna have a success rate of around 95%.
Provisional data suggests that the Oxford-AstraZeneca vaccine has an average efficacy of 70.4 percent, a figure that could reach 90 percent if the dose is adjusted.
“The results show that the vaccine is effective against COVID-19, including no severe infection and no hospitalization in the vaccine group,” said Pascal Soriot, CEO of AstraZeneca.
Efficacy rates vary because preliminary data examined two different ways of administering the vaccine.
In one group, the patients were given a placebo which consisted of a smaller initial dose of the vaccine followed by a larger booster dose a month later. Surprisingly, analysis of the data revealed that the vaccine was around 90% effective in preventing COVID-19 in this group.
In the second group, patients received the same dose in both cases, producing a 62.1% lower efficacy rate.
It is not yet clear why a smaller starting dose works better. But scientists have suggested that it could be because a higher initial dose causes the body to produce antibodies against the vaccine itself.
Another reason could be that a smaller initial dose triggers memory cells, preparing the body to produce antibodies in larger amounts when the second higher dose is given.
The Pfizer-BioNTech and Moderna vaccines are based on messenger RNA (mRNA) technology.
The Oxford-AstraZeneca is different – it’s an adenovirus vector vaccine taken from a cold that normally infects chimpanzees.
Although it has been genetically engineered to prevent infection in humans, it only carries part of the coronavirus called ‘spike protein’.
Once the vaccine is injected into human cells, it triggers an immune response against spike proteins, producing antibodies and memory cells that destroy infected cells.
The Medicines and Health Products Regulatory Authority (MHRA) in the UK must now decide which dose to use if it approves the vaccine for emergency use.
But in hard-hit India, the government is stepping up its review of COVID-19 vaccines developed by Oxford-AstraZeneca and Pfizer-BioNTech.