Flu (Influenza): Symptoms, Risks and the Flu Vaccine

In short: Flu (influenza) is a viral infection of the nose, throat and lungs. Most healthy people recover in about a week, but flu can cause severe illness, hospital admission and death in older people, babies, pregnant women and people with long-term conditions. A yearly flu vaccine is the best protection. For the 2026 to 2027 season, the NHS programme for children and pregnant women starts on 1 September and for adults aged 65 and over and adults in risk groups on 1 October.

This guide, written by a Ready Health prescribing pharmacist and checked against the UKHSA Green Book and the 2026 to 2027 annual flu letter, explains flu symptoms, who is eligible for a free vaccine and what to expect.

What is influenza?

Flu is caused by influenza viruses. Types A and B cause the seasonal outbreaks seen every winter in the UK. Influenza A viruses also circulate in animals such as birds and pigs, and occasionally a new strain spreads to people, which is how flu pandemics start. Flu viruses change constantly, which is why the vaccine is updated every year.

Flu spreads through droplets from coughs and sneezes and by touching contaminated surfaces and then your eyes, nose or mouth. Symptoms usually start one to three days after infection, and people are most infectious in the first few days of illness.

What are the symptoms of flu?

Flu tends to come on suddenly. Common symptoms include:

• a high temperature, chills and sweats
• aching body and exhaustion
• dry cough and sore throat
• headache
• loss of appetite, difficulty sleeping, and in children, sometimes stomach upset or earache

Is it flu or a cold?

Colds usually come on gradually and mainly affect the nose and throat; you can generally carry on with day-to-day activities. Flu usually starts abruptly and leaves you feeling too unwell to do much.

When should I get medical help for flu?

Most people can manage flu at home with rest, fluids and paracetamol or ibuprofen if suitable. Contact your GP or NHS 111 if symptoms are getting worse or not improving after a week, if you are pregnant, 65 or over, or have a long-term condition or weakened immune system, or if you are worried about a baby or child. Call 999 if someone has severe difficulty breathing, chest pain, blue or grey lips, or is very drowsy or confused.

Antiviral medicines may sometimes be prescribed for people at high risk of complications, ideally early in the illness. Antibiotics do not treat flu itself.

Who can get a free flu vaccine in 2026 to 2027?

Eligibility in England is unchanged from last season.

Clinical risk groups include long-term heart, lung, kidney, liver or neurological conditions, diabetes, a weakened immune system, a missing or poorly functioning spleen, and a BMI of 40 or above. Most vaccinations should be completed by the end of November, although the vaccine can still be given later in the season.

Which flu vaccine will I be offered?

The UK uses different vaccines for different age groups, chosen to give the best protection:

• Most children aged 2 to 17: a nasal spray vaccine, which is quick and painless. Children who cannot have it, for medical reasons or because it contains porcine gelatine, may be offered an injection instead.
• Adults aged 18 to 64: an injected vaccine, made using cell-culture or recombinant technology.
• Adults aged 65 and over: an injected vaccine designed to produce a stronger response in older people, such as an adjuvanted, high-dose or recombinant vaccine.

You do not normally need to choose; the vaccinator will use the right vaccine for your age and health.

Is the flu vaccine safe?

Flu vaccines are given to millions of people in the UK every year. The injected vaccine cannot give you flu. Side effects are usually mild and short-lived, such as a sore arm, a slightly raised temperature or aching muscles for a day or two. The nasal spray can cause a runny or blocked nose. Serious allergic reactions are very rare. People with egg allergy can usually still be vaccinated; tell the vaccinator about any allergies.

Frequently asked questions

Why do I need a flu vaccine every year?

Flu viruses change from year to year and protection from the vaccine fades over time, so a new vaccine is made each season to match the strains expected to circulate.

Can I have the flu vaccine if I am not eligible on the NHS?

Yes. Many people choose to have a flu vaccine privately, for example through a pharmacy, clinic or employer scheme. A clinician will check it is suitable for you first.

Can I have the flu and COVID-19 vaccines at the same time?

Yes, if you are eligible for both they can usually be given at the same appointment.

Is the flu vaccine safe in pregnancy?

Yes. It is recommended at any stage of pregnancy and helps protect the baby in the first months of life.

Key takeaways

• Flu is more than a bad cold and can be serious for people at higher risk.
• A yearly vaccine is the best protection; eligibility for 2026 to 2027 is unchanged.
• Children and pregnant women can be vaccinated from 1 September; adults aged 65 and over and adults in risk groups from 1 October.
• Get medical help if symptoms are severe, worsening or you are in a higher-risk group.

Sources and further reading

• UKHSA, NHS England and DHSC: National flu immunisation programme 2026 to 2027 letter
• UKHSA Green Book, chapter 19: Influenza
• NHS: Flu vaccine
• NHS: Flu

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

Looking for a flu vaccination in Standish, Wigan, Chorley or Bolton? Ready Health offers vaccination appointments for individuals and workplaces, and a clinician will check that the vaccine is suitable for you. You can book a vaccination appointment online.