Types of COVID-19 Vaccine: mRNA, Protein-Based and the 2026/27 Update Explained

Two kinds of COVID-19 vaccine are in use in the UK this winter: mRNA vaccines, which most people are offered, and a protein-based vaccine kept for people who cannot have mRNA. Both have been updated for 2026/27, but they work in different ways, contain different ingredients and are matched to slightly different lineages of the virus.

This guide explains the types of COVID vaccine in use: how each one works, what is in it, which one each age group is offered and which one we use. It is part of our guide to the 2026/27 COVID-19 booster, which covers how well this season’s vaccine protects and who it matters most for.

mRNA vaccines: a set of instructions, not the virus

An mRNA vaccine contains no virus at all. Its active ingredient is a strand of messenger RNA, the molecule our cells use to carry instructions for making proteins. The vaccine’s mRNA carries the code for the coronavirus spike protein, with two small changes that hold the protein in the shape it has before it attaches to a cell. That is the shape the immune system most needs to recognise.

The mRNA is made in a laboratory from a DNA template, without growing any virus, eggs or cells. It is wrapped in a lipid nanoparticle, a microscopic droplet of fat that protects it and carries it into cells. After the injection, cells near the injection site take up the droplets, read the instructions and display the spike protein for a short time. The immune system responds with neutralising antibodies, which can stop the virus entering cells, and with T cells, which help to clear infection and support longer-term memory. The body breaks the mRNA down within a few days. It works outside the cell nucleus, so it cannot alter your DNA.

Because only the genetic code changes from season to season, the vaccine can be updated to a new lineage each year. The lipid coating contains polyethylene glycol (PEG), a compound also found in some laxatives, bowel preparations, depot steroid injections and cosmetics. A confirmed allergy to PEG is rare, but it is one of the few reasons an mRNA vaccine may not be suitable.

Protein-based vaccines: the target delivered ready-made

A protein-based vaccine skips the instruction step. Instead, the spike fragment is manufactured in advance and injected as it is, so your immune system meets the target straight away. The UK’s protein-based COVID-19 vaccine uses the receptor binding domain, the part of the spike that latches on to human cells, with two copies joined together.

To strengthen the immune response, the vaccine includes an adjuvant. Its adjuvant contains an oil called squalene, similar to the adjuvant in the flu vaccine many older adults have had, along with polysorbate 80. The vaccine contains no PEG, which is one reason it can be an option for people who cannot have an mRNA vaccine.

This season’s protein-based vaccine is matched to LP.8.1, another lineage from the same JN.1 family as XFG. The NHS keeps it for people aged 12 and over who cannot have an mRNA vaccine, and that call is made person by person. Its most common side effects are a sore arm, headache, tiredness and aching muscles, mostly mild to moderate and over within a few days.

mRNA and protein-based vaccines compared

Neither type is better for everyone. JCVI, which advises the UK governments on vaccines, has no preference between products for adults. It does want the programme to include more than one type, so that people who cannot have one can have another, and it advises using the most recently updated vaccine whenever that does not delay a campaign.

Who gets which vaccine in 2026/27

Different mRNA products have slightly different reported rates of myocarditis, and national guidance takes this into account when it chooses vaccines for children and young people, and for anyone who has had heart inflammation after an earlier dose.

Who is offered a free NHS vaccine this winter is a separate question from which vaccine is used, and NHS inform sets out the groups for Scotland. Bruntsfield Pharmacy explains who qualifies for a free COVID-19 vaccine in Scotland.

Which vaccine we use, and whether your history matters

At Edinburgh Vaccination Clinic we use an mRNA vaccine, this season’s version matched to XFG, licensed from age 12 and given as a single dose. We do not stock the protein-based vaccine. You are welcome to ask the name of the product at your appointment.

It does not matter which vaccines you have had before. A dose this season works as a booster whatever product you had last time, including vaccines given abroad, which may have been a different type altogether, such as an inactivated whole-virus vaccine. Mixing products is safe and produces a good immune response, although switching can bring a stronger short-term reaction than staying with the same one. The gap since your last dose needs to be at least three months, whichever product it was.

If you have had a serious reaction to an mRNA vaccine before, or have an allergy to PEG, we will talk through whether an mRNA vaccine is suitable before going ahead. Our guide to COVID-19 vaccination in pregnancy, with a weakened immune system or with allergies explains the precautions.

The 2026/27 update: why XFG?

The spike protein changes as the virus evolves, and antibodies made against an older version recognise a newer one less well. Each year the vaccines are updated towards the lineage expected to matter most in the coming season. XFG became the most common lineage in the UK in the summer of 2025 and was still the most common in October 2026, so this season’s mRNA vaccines are built around its spike. The protein-based vaccine is matched to LP.8.1, a related lineage from the same family.

The match does not need to be perfect to be useful. When the virus has drifted in the past, protection against severe illness has tended to hold up better than protection against infection. Surveillance teams track newer lineages such as BA.3.2, which the World Health Organization currently rates as low risk, and the vaccines are reviewed again every year.

How to get started

1. Book online. Use the booking calendar on this page or call 0131 563 6824. See our COVID-19 vaccination page and vaccine prices page for details.
2. Complete a short health check. We ask about allergies, including to PEG, past reactions, the vaccines you have had and anything that affects your immune system.
3. Attend your appointment. If an mRNA vaccine is right for you, it is given as a single injection into the upper arm.
4. Leave with aftercare advice. We explain what to expect and which symptoms mean you should get help.

Types of COVID-19 vaccine: your questions answered

Is one type of COVID-19 vaccine better than the other?

For adults, JCVI has no preferred product. Both types are updated each season and both are used to protect against serious illness. Which one is right for you depends mainly on whether you can have an mRNA vaccine.

Can I choose the protein-based vaccine instead of mRNA?

In the NHS programme the protein-based vaccine is used when an mRNA vaccine is not clinically suitable, which is decided for each person individually. We do not stock it, so if you think you may need it, your GP or specialist can advise.

Does it matter which COVID-19 vaccine I had before?

No. This season’s dose boosts your protection whichever product you had last time, including vaccines given abroad. Changing product is safe, although it can bring a stronger short-term reaction.

Are mRNA vaccines made using eggs or animal cells?

No. The mRNA is produced in a laboratory from a DNA template, without growing virus, eggs or cells, so an egg allergy is not a reason to avoid it.

Why does the protein-based vaccine contain an adjuvant?

The adjuvant strengthens the immune response to the protein. The one used in the UK’s protein-based COVID-19 vaccine contains squalene, an oil also found in the adjuvanted flu vaccine, and polysorbate 80.

Why do children have a different strength of vaccine?

Children aged 5 to 11 produced antibody levels comparable to young adults on a lower dose, with slightly fewer reactions, so a children’s-strength version is used from 6 months to 11 years. From age 12 the adult-strength vaccine is used.

What happens if a different variant takes over this winter?

When the virus has changed in the past, protection against serious illness has tended to hold up better than protection against infection. UKHSA and the World Health Organization track new lineages closely, and the vaccines are reviewed every year.

For how well this season’s vaccine protects and for how long, read our guide to the 2026/27 COVID-19 booster. For what to expect afterwards, see COVID-19 vaccine side effects.

This page gives general information and is not a substitute for a personal clinical assessment. COVID-19 vaccines are prescription-only medicines, so we check that vaccination suits you before giving one. For side effects, speak to your pharmacist or GP, or call NHS 24 on 111. In an emergency, call 999.

Sources: UKHSA, Immunisation against infectious disease (the Green Book), chapter 14a, COVID-19, 10 September 2026; Scottish Government, SGHD/CMO(2026)18, 21 September 2026; JCVI statement on COVID-19 vaccination in autumn 2026 and spring 2027, 16 July 2025; UKHSA blog, 8 October 2026; Summary of Product Characteristics for the XFG-adapted 30 microgram mRNA vaccine (electronic medicines compendium).