Coronavirus: how the Pfizer Covid-19 vaccine works

The experimental vaccine leading the race to provide coronavirus immunity depends on an entirely new approach to preventative medicine.

Indeed, if such a vaccine “was approved for coronavirus, it would be the first of its type” to deliver a successful immunisation, research magazine Horizon reported back in April.

Although the breakthrough injection – developed by the US drug company Pfizer and German research lab BioNTech – has not yet been approved, it has been shown to be 90% effective in protecting people from Covid-19.

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 – which is still undergoing Phase 3 trials – 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”.