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About The Coronavirus Vaccine

UK regulators have authorised a covid-19 vaccine created by Pfizer and its partner BioNTech for emergency use, meaning that vaccine rollout is planned to begin soon. Here, we answer questions about the science of the vaccine, who will get it first, how confident we can be in the authorisation process and the logistics of vaccinating everyone in the UK.

Science

How effective is the vaccine?

About 95 per cent. The phase 3 trials of the Pfizer/BioNTech vaccine involved 42,000 people, about half of whom got the experimental vaccine and the rest a placebo. In total, 170 people fell ill with covid-19. Only eight of them were in the vaccine group; 162 had received the placebo. So around 5 per cent of cases were in the vaccine group, which is where the 95 per cent figure comes from. That is a very healthy number: the World Health Organization (WHO) has said it would be happy with 50 per cent.

What is in the vaccine?

The active ingredient is messenger RNA that carries instructions for making the virus’s spike protein, which it uses to gain entry to cells. The mRNA is synthetic, not extracted from actual viruses. It is delivered in a tiny sphere of inert fatty material called a lipid nanoparticle.

The RNA-bearing nanoparticles are suspended in saline solution and injected into muscle tissue in the upper arm. The mRNA is then taken up by specialist immune cells, which follow its instructions to make the spike protein, just as they would do if they had become infected with the actual virus.

The spike protein is recognised as foreign by the immune system, which mounts an attack against it. Antibodies, B cells and T cells are activated, according to Uğur Şahin, the chief executive of the small German company BioNTech that co-developed the vaccine with US drug giant Pfizer. An immune memory is also laid down, he says, which means the immune system has learned how to defeat the pathogen and is primed to mount a swift response if it encounters the coronavirus again.

How long does the immune memory last?

It’s hard to say at this point, because the clinical trials weren’t set up to answer that question, and in any case, they only began dispensing second doses of the vaccine four months ago. The WHO says that a minimum of six months would be acceptable. It will become clearer as time marches on and the volunteers continue to be monitored. Sahin says he expects protection to last “months or even years”. Given what we know about natural immunity that looks about right, says Eleanor Riley at the University of Edinburgh in the UK. She envisages people needing annual boosters, at worst.

How long does it take for immunity to develop fully after vaccination?

The trial began assessing immunity seven days after the second shot. We know that protective immunity builds up within four weeks of the first dose, but Sahin says that it appears to develop earlier than that. Further details will be published in a matter of days, he says.

What happens to the mRNA in the body?

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It is active for a few days then decays rapidly.