People Vaccinated in the UK (1st dose): 52,399,031

People Vaccinated in the UK (2nd dose): 48,520,906

The Pfizer / BioNTech COVID-19 vaccine was developed by BioNTech (a German biotechnology company) in cooperation with Pfizer (an American pharmaceutical corporation).

It was the first COVID-19 vaccine to be approved by the UK’s Medicines and Healthcare products Regulatory Agency. The decision was made with advice from the Commission on Human Medicines (CHM), the government’s independent expert scientific advisory body.

mRNA (part of virus genetic code)
NHS availability
MHRA Approval

2 December 2020

How does the Pfizer / BioNTech vaccine work in the body when taken?

The jabs are known as a messenger RNA (mRNA) vaccine. It uses synthetically produced genetic material called mRNA, which encodes the instructions to produce the SARS-CoV-2 (COVID-19) spike protein (the part of the virus that allows it to enter human cells).

The injection inserts this mRNA into the body. This then enters cells, which read the genetic code and start producing the virus protein – thus triggering a response by the immune system and coaching it to fight a future infection.

The mRNA molecule is not injected directly into the body, but is wrapped in oily bubbles made of lipid nanoparticles, to prevent our natural enzymes from breaking it down.

The jab uses mRNA produced in the lab by a template DNA, and doesn’t use a virus, unlike conventional vaccines which are produced using weakened forms of the virus. This can make the rate at which it can be produced or modified dramatically accelerated.

What are the ingredients of the Pfizer / BioNTech vaccine?

This vaccine contains polyethylene glycol/macrogol (PEG) as part of ALC-0159.

The other ingredients are:

Potassium dihydrogen phosphate




Sodium chloride

Potassium chloride

Disodium hydrogen phosphate dihydrate


ALC-0159 = 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide

ALC-0315 = (4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate)

You should not take the vaccine if you have ever had a severe allergic reaction to any of the active substances or any of the other ingredients.


How is the Pfizer / BioNTech vaccine administered?

The Pfizer / BioNTech vaccine is only being administered to people in a safe health care environment with facilities to treat allergic reactions if they do occur. Do not take the vaccine from anyone else. If offered by anyone, and you are in doubt, contact your GP.

This vaccine is given after dilution as an injection of 0.3 mL into a muscle of your upper arm.

You will receive 2 injections (of the same vaccine), given at least 21 days apart.

Protection against COVID-19 disease may not be maximally effective until at least 7 days after the second dose.

During and after each injection of the vaccine, your doctor, pharmacist or nurse will watch over you for around 15 minutes to monitor for signs of an allergic reaction.


Are there any possible risks and/or side effects of the Pfizer / BioNTech vaccine?

Nothing in medicine comes without risks – even something we take without thinking, like paracetamol, may pose a risk.

Like all vaccines, the Pfizer / BioNTech vaccine can cause side effects, although not everybody gets them.

Most side effects are mild or moderate and go away within a few days of appearing. If side effects such as pain and/or fever are troublesome, they can be treated by medicines for pain and fever such as paracetamol.


Side effects can include:

Very common (may affect more than 1 in 10 people)


Muscle pain, joint pain, pain at the injection site




Common (may affect up to 1 in 10 people)

Swelling at the injection site

Redness at the injection site


Uncommon (may affect up to 1 in 100 people)

Feeling unwell

Enlarged lymph nodes

Rare (may affect up to 1 in 1000 people)

Temporary one-sided facial drooping (Bell’s palsy)

Frequency unknown

Severe allergic reactions (anaphylaxis)

Warnings and Precautions

Talk to your doctor, pharmacist or nurse before you are given this vaccine if you:

Ever had a severe allergic reaction or breathing problems after any other vaccine injection or after you were the vaccine in the past.

A severe illness with high fever. However, a mild fever or upper airway infection, like a cold, are not reasons to delay vaccination.

A weakened immune system, such as due to HIV infection, or are on a medicine that affects your immune system.

A bleeding problem, bruise easily or use a medicine to inhibit blood clotting.

Do NOT take the vaccine if

you are allergic to the active substance or any of the other ingredients of this vaccine


Signs of an allergic reaction may include itchy skin rash, shortness of breath and swelling of the face or tongue. Contact your doctor or healthcare professional immediately or go to the nearest hospital emergency room right away if you have an allergic reaction. It can be life-threatening.

As with any vaccine, this vaccine may not fully protect all those who receive it.

No data is currently available in individuals with a weakened immune system or who are taking chronic treatment that suppresses or prevents immune responses.

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