The flu jab (and nasal spray flu vaccine)
Influenza vaccine
A vaccine given each year to help protect against seasonal flu (influenza).
What is Influenza vaccine?
The influenza vaccine, often called the flu jab, is given each year to help protect against seasonal flu, an infection that can be serious for older people, young children, pregnant women and those with certain health conditions. It works by helping the immune system recognise and fight flu viruses. Most adults have an injection, while many children are offered a nasal spray, which is a live vaccine. Side effects are usually mild, such as a sore arm or feeling a bit off-colour. Some products are made using eggs, so egg allergy is checked.
Education and reference only. This is a plain-language guide to Influenza vaccine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
The influenza vaccine is a vaccine given each year, through the UK health service, to help protect against seasonal flu, an infection caused by flu viruses that can make people very unwell and is especially risky for older people, young children, pregnant women and those with long-term health conditions. Most adults receive it as an injection, while many children are offered it as a nasal spray instead. The viruses circulating change each year, which is why a new vaccine is given each season. It is a preventive measure rather than a treatment for flu you already have.
How it works
Vaccines work by showing the immune system a safe, harmless version or part of a virus so it learns to recognise it. The influenza vaccine prompts the body to make defences against the flu viruses expected that season, so that if you meet the real virus your immune system can respond quickly and you are less likely to become seriously ill. Because flu viruses change from year to year, the vaccine is updated and given each season. The nasal spray used in children is a live but weakened vaccine that works in a similar way through the lining of the nose.
Company & origin
Originated / developed by: Various manufacturers.
Vaccines used across the UK each year, through the UK health service, to protect against seasonal flu, given as an injection or, for many children, a nasal spray.
Practical use
How to take Influenza vaccine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Have it each autumn, following the UK immunisation schedule, as protection needs renewing every flu season.
- Most adults have an injection; many children are offered a nasal spray instead.
- Tell the nurse or pharmacist about any serious egg allergy, as an egg-free injected option can be used.
- Mention a weakened immune system, or wheezing or active asthma in a child, as the nasal spray may not be suitable.
- Stay for any brief observation advised, and report any unexpected reaction.
Weighing it up
Advantages & disadvantages of Influenza vaccine
Advantages
- Helps protect against seasonal flu, which can be serious in at-risk groups.
- Offered free within the UK health service to those most at risk, and updated each year.
- Available as an injection for adults and a needle-free nasal spray for many children.
Disadvantages
- Needs to be given every year, as flu viruses change and protection fades.
- Can cause mild, short-lived effects such as a sore arm or feeling off-colour.
- Some injected products are made using eggs, and the children's nasal spray is a live vaccine needing care in some people.
Practical use
Good to know
The most useful thing to know is that flu changes each year, so the vaccine is given every autumn to keep protection up to date, and it is offered free within the UK health service to those most at risk. It cannot give you flu, although you may feel a bit off-colour for a day or two afterwards. Side effects are usually mild, such as a sore arm where the injection was given, or a mild temperature. A few points need a little care: some injected vaccines are made using eggs, so a serious egg allergy is checked and an egg-free option can be used; and the children's nasal spray is a live vaccine, so it is used with caution in children with weakened immune systems or with wheezing or active asthma, where an injection may be chosen instead. Follow the UK immunisation schedule and advice for who should have it and when.
Who should not take it / use with caution
- People who have had a serious allergic reaction to a previous flu vaccine or to an ingredient should not have that vaccine.
- The live nasal spray is used with caution, or avoided, in children with weakened immune systems or with wheezing or active asthma.
- Anyone who is unwell with a high temperature should usually wait until they have recovered.
Monitoring
- A brief period of observation after vaccination where advised.
- Checking for any allergic reaction, particularly in those with relevant allergies.
- Following the UK immunisation schedule each year to keep protection up to date.
Side effects
- A sore, red or swollen arm where the injection was given.
- Feeling a bit off-colour, with a mild temperature, tiredness or aches for a day or two.
- With the nasal spray, a runny or blocked nose; rarely, allergic-type reactions to any vaccine.
Key interactions
- It can be given alongside many other vaccines; the team will advise on timing.
- Tell the team about medicines that weaken the immune system, which can affect which vaccine is suitable.
- There are few routine medicine interactions, but always mention all your medicines.
Available as: An injection for most adults; a nasal spray for many children.
Answers
Influenza vaccine: frequently asked questions
What is the flu vaccine for?
It is given each year to help protect against seasonal flu, which can be serious for older people, young children, pregnant women and those with health conditions.
Can the flu jab give me flu?
No. The vaccine cannot give you flu, although you may feel a bit off-colour or have a sore arm for a day or two afterwards.
Why do I need it every year?
Flu viruses change from year to year and protection fades, so a new, updated vaccine is given each autumn.
I am allergic to eggs — can I have it?
Some injected vaccines are made using eggs, so tell the nurse about a serious egg allergy; an egg-free option can usually be used.
Is the children's nasal spray different?
Yes, it is a live but weakened vaccine given as a spray; it is used with caution in children with weakened immune systems or active wheezing or asthma.
The wider class
About Vaccine (seasonal influenza)
Influenza vaccine belongs to the vaccine (seasonal influenza) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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