The Pfizer/BioNTech coronavirus vaccine beat its rivals to be the first to be approved for use in the UK — but jabs from Moderna and Oxford/Astrazeneca have since joined the Pfizer jab in gaining authorisation.
The UK made history when grandmother Margaret Keenan, 90, became the first patient in the world to receive the Pfizer Covid-19 jab following its clinical approval.
Since Margaret millions of jabs have now been administered across the UK but second jabs have been delayed to get the most amount of vulnerable people some protection as soon as possible.
So what are the differences between the vaccines?
Watch: COVID-19 vaccines - How do the Moderna, Pfizer and Oxford coronavirus jab candidates compare?
The Pfizer jab is a messenger RNA (mRNA) vaccine.
Conventional vaccines are produced using weakened forms of the virus, but mRNAs use only the virus’s genetic code.
An mRNA vaccine is injected into the body where it enters cells and tells them to create antigens. These antigens are recognised by the immune system and prepare it to fight coronavirus.
No actual virus is needed to create an mRNA vaccine. This means the rate at which it can be produced is dramatically accelerated.
As a result, mRNA vaccines have been hailed as potentially offering a rapid solution to new outbreaks of infectious diseases.
In theory, they can also be modified reasonably quickly if, for example, a virus develops mutations and begins to change.
mRNA vaccines are also cheaper to produce than traditional vaccines, although both will play an important role in tackling Covid-19.
One downside to mRNA vaccines is that they need to be stored at ultra-cold temperatures and cannot be transported easily.
The Moderna vaccine works in a very similar way to the jab from Pfizer/BioNTech.
Coronavirus is studded with “spike proteins” that it uses to enter human cells. Covid-19 vaccines target this spike protein.
The Moderna and Pfizer vaccines use synthetic messenger RNA (mRNA), a genetic material that contains information about the spike protein.
The vaccines provide the body with instructions to produce a small amount of this protein which, once detected by the immune system, leads to a protective antibody response.
Moderna’s vaccine does not require the same ultracold storage as Pfizer’s and can remain stable at normal fridge temperature for 30 days.
Trials on more than 30,000 people in the US have shown the Moderna jab to be 94 per cent effective in preventing coronavirus.
Moderna has not identified any significant safety concerns and its vaccine has been approved for use in the US.
The MHRA accepted the recommendation of the Commission on Human Medicines and authorised the Moderna vaccine on January 8.
The vaccine developed by the University of Oxford and pharmaceutical giant AstraZeneca was approved by the MHRA in December last year.
The Oxford jab is not an mRNA vaccine, instead it uses a harmless weakened version of a virus that causes the common cold in chimpanzees.
Oxford data indicates the vaccine has 62% efficacy when one full dose is given followed by another full dose, but when people were given a half dose followed by a full dose at least a month later, its efficacy rose to 90%.
The combined analysis from both dosing regimes resulted in an average efficacy of 70.4%.
How does the AstraZeneca/Oxford vaccine work?