How does the Pfizer coronavirus vaccine work?

The UK has become the first country in the world to approve a coronavirus vaccine for widespread use after regulators gave the green light to the Pfizer-BioNTech jab.

The Medicines and Healthcare products Regulatory Agency (MHRA) approved the vaccine on Wednesday, after the body was given power to approve the drug by the government under special regulations.

Albert Bourla, the chairman and chief executive officer of Pfizer, said the UK’s decision “marks a historic moment in the fight against Covid-19”, adding that “science will win”.

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How was it approved?

Pfizer was the first company to announce highly promising results from its Phase 3 trials, revealing that the jab has around 95% efficacy.

Concerns were raised over the fact that the drug must be stored at -70C, posing a practical challenge for health services, but the UK nevertheless bought 40m doses and granted the MHRA special powers to approve the jab at unprecedented speed.

No. 10 has now said the vaccine has been given the green light and will be rolled out across the UK from early next week, while Scottish first minister Nicola Sturgeon said Scotland’s first doses will be administered on Tuesday.

“Batch testing has been completed this morning for the first deployment of 800,000 doses of the vaccine,” Health Secretary Matt Hancock told the Commons today. “This is a day to remember in a year to forget,” he added.

Hancock has vowed to launch an extensive “public information campaign” to boost trust in the vaccine’s safety following concerns that efforts to achieve herd immunity among the population will be undermined by vaccine sceptics, and has even vowed to take the vaccine live on air to prove it was safe.

In a further attempt to reassure the public, MHRA chief Dr June Raine this morning insisted that “no corners have been cut” in approving the vaccine, despite vaccines usually taking “around a decade from start to finish before they hit the shelves”, City A.M. reports.

“Our expert scientists and clinicians have worked round the clock, carefully and methodically poring over tables, analyses and graphs on hundreds of thousands of pages of data,” Raine said. “The safety of the public will always come first”.

How does it work?

Most vaccines rely on weakened or inactivated parts of the virus to provoke an immune response in their recipients, but the Pfizer version is synthetic.

The new vaccine is made using messenger ribonucleic acid (also known as messenger RNA or mRNA). Whereas DNA is where we store our genetic information, mRNA - as its name suggests - transmits information and helps to determine how our genes are expressed.

To put that another way, mRNA “essentially puts DNA instructions into action”, says Horizon.

In the case of the Pfizer vaccine, the researchers synthesised a form of mRNA that will “cause our own cells to make a viral protein” from the Covid-19 coronavirus, says The New York Times.

The protein is harmless in isolation, but prompts the human immune system to “make antibodies and immune cells that can recognise the protein quickly and deliver a swift attack”, the newspaper adds.

Since the active ingredient in the vaccine - the mRNA - is “made from a DNA template in a lab”, says Pfizer, scaling up production is “a more rapid process than [with] conventional vaccines and a major advantage when it comes to sudden pandemics”.