NEWS EMERGED THIS morning that the UK has formally approved a vaccine against Covid-19 from pharmaceutical giant Pfizer and German biotech company BioNTech.

The vaccine has been authorised by the UK’s Medicines and Healthcare Products Regulatory Authority for emergency use, and is expected to start rolling out by the end of the year.

Pfizer chairman Albert Bourla said it was a “historic moment in the fight against Covid-19″, and there has been much celebration at the news.

Approval means the UK can begin rolling out the vaccine to those most in need, including frontline workers, and an analysis shows that the vaccine can prevent 95% of people from getting Covid-19, including 94% in older age groups.

Here’s how it works.

What type of vaccine is this?

The jab is known as 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.

What are the advantages of this type of vaccine?

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.

Are they safe?

All vaccines undergo rigorous testing and have oversight from experienced regulators.

Some believe mRNA vaccines are safer for the patient as they do not rely on any element of the virus being injected into the body.

mRNA vaccines have been tried and tested in the lab and on animals before moving to human studies.

The human trials of mRNA vaccines – involving tens of thousands of people worldwide – have been going on since early 2020 to show whether they are safe and effective.

Pfizer will continue to collect safety and long-term outcomes data from participants for two years.