Quick answer
What is flu vaccine used for?
The flu vaccine is an annual vaccination that reduces your risk of catching flu and its serious complications. In the UK it is offered free on the NHS each autumn to people at higher risk, including over 65s, pregnant women, and those with long-term conditions, while others can pay for it at a pharmacy.
Why the flu vaccine matters
Influenza (flu) is not just a bad cold — it can cause serious illness, hospital admission and death, especially in older adults, pregnant women, and people with long-term health conditions. The annual flu vaccine is the most effective way to reduce your risk. It is updated each year to match the strains expected to circulate.
Who is eligible for a free NHS flu vaccine
The NHS offers free flu vaccination each autumn to groups at higher risk, which typically include:
- all adults aged 65 and over
- pregnant women, at any stage of pregnancy
- people with long-term conditions such as asthma, COPD, diabetes, heart disease, kidney disease, liver disease, neurological conditions, or a weakened immune system
- carers and care home residents
- frontline health and social care workers
- children, who receive a nasal spray vaccine — aged 2–3 through the GP, and school-aged children through school programmes
Eligibility is updated each year, so check NHS flu vaccine guidance for the current season. If you are not eligible for a free vaccine, pharmacies offer paid vaccination, usually costing £10–£20.
Types of flu vaccine available
The injected vaccine (inactivated) is the standard option for most adults. It contains killed virus fragments and cannot cause flu.
The nasal spray (live attenuated) is used for children. It contains weakened live virus and may cause a mild runny nose but not full flu illness.
Enhanced vaccines are higher-dose or adjuvanted vaccines used for older adults, offering a stronger immune response.
How and when to get the flu vaccine
You can book the flu vaccine through your GP surgery, pharmacy, or maternity service if you are pregnant. The best time is September to October, before flu season peaks, though vaccination later in winter still helps. It takes about two weeks after vaccination to develop full protection.
Side effects of the flu vaccine
Most people have no serious side effects from the flu vaccine. Common effects include a sore arm at the injection site for a day or two, mild aching or a slight fever, and, in children, a runny nose after the nasal spray.
Serious allergic reactions (anaphylaxis) are very rare. You may be asked to stay at the vaccination site for a few minutes if you have a history of severe allergies.
Flu vaccine and egg allergy
Most flu vaccines are grown in eggs and contain tiny amounts of egg protein. Most people with egg allergy can be safely vaccinated — including those with severe allergy — often with observation afterward. Tell the vaccinator about any allergies.
Flu vaccine vs catching flu naturally
Natural infection provides immunity but at the cost of illness risk — including pneumonia, hospitalisation, and death in vulnerable people. Vaccination provides protection without that risk. It also reduces spread to vulnerable contacts.
Flu vaccine and COVID-19
You can have flu and COVID-19 vaccines at the same appointment if offered. Both are recommended for eligible groups — they protect against different viruses.
If you think you have flu after vaccination
The injected vaccine cannot cause flu. If you develop flu-like symptoms after vaccination, you may have caught flu before the vaccine took effect, or another virus such as a cold. See our flu guide for symptoms and when to seek help.
Common questions about flu vaccine
- Who gets the flu vaccine free on the NHS?
- The flu vaccine is free for adults aged 65 and over, pregnant women, people with long-term conditions such as asthma, diabetes or heart disease, carers, care home residents, frontline health and social care workers, and children in eligible age groups. Eligibility can change, so it is worth checking current NHS guidance each year.
- Can the flu vaccine give you flu?
- No, the standard injected flu vaccine cannot give you flu because it contains inactivated (killed) virus. The nasal spray given to children contains weakened live virus, which may cause mild cold-like symptoms but not full flu illness.
- When should I have the flu vaccine?
- The flu vaccine is best had in autumn, from September to October, before flu typically peaks in winter. It takes about two weeks to build full protection, though having it later in winter still helps if you have not yet been vaccinated.
- What are the side effects of the flu vaccine?
- Common side effects of the flu vaccine include a sore arm at the injection site, mild aching, and a slight temperature for a day or two. Serious allergic reactions are very rare, and the benefits for at-risk groups far outweigh these mild effects.
- Does the flu vaccine work every year?
- The flu vaccine's effectiveness varies each year depending on how well the vaccine strains match the circulating flu virus. Even when it is not a perfect match, vaccinated people who catch flu usually have milder illness and are less likely to need hospital care.