Flu Jab: Who Should Have It, Benefits, and Side-Effects

Influenza (flu) is a common viral infection that tends to be most common in the winter. Flu can cause much more severe symptoms than the common cold. Some people can become seriously ill with flu, needing hospital treatment, and it can be life-threatening. Certain groups of people, such as older adults and young children, are at higher risk from flu infection.

Getting the flu vaccine reduces the risk of catching flu, and also reduces the chances of becoming seriously unwell with flu. Exactly how well it works differs from year to year.

Every year, the strains of influenza (flu) that cause infection change. This is because viruses are constantly mutating in order to increase their chances of causing infection. (If the flu virus stayed the same, then everyone who had been exposed to it would be immune. The flu virus would therefore be less able to infect people and its numbers would reduce rather than increase. All viruses have evolved to try and increase their own numbers constantly by infecting people and therefore replicating).

Expert scientists and the World Health Organization (WHO) monitor flu viruses throughout the world and predict which flu strains they think are going to be the most active each year and therefore which strains are to be included in the current year’s vaccine. This is done by looking at data from previous years but also looking at data from other countries, like Australia, where the flu season is ahead of that in the UK. They then develop a vaccine to try and protect against these particular strains.

If 10 people have the flu jab, it usually provides protection from flu for 7 or 8 of them. If the vaccine does not match the predicted flu types around that year, the protection rate can be lower. For example, in 2025-2026 the predictions by the scientists were less good than usual and the vaccine only protected between 2 and 3.4 in 10 adults and between 5 and 7 in 10 children. Even with this less effective vaccine, it is estimated that 104,000 hospital admissions and 7,100 deaths were prevented that winter.

The flu vaccine provides protection for about 6 months, so flu vaccines are offered annually. In the UK, flu vaccines are usually available from October onwards, though they are available from September for some groups.

For the 2025-26 season, flu vaccines for eligible children and pregnant women will be available from 1st September 2026. Flu vaccines for other groups of eligible adults (see below) will be available from 1st October 2026.

It’s better to have the flu vaccine before flu starts spreading, because it takes about two weeks for the vaccine to start to provide protection. Flu season usually starts in December and lasts until early March.

The flu injection is made from the three strains of flu virus that are most likely to cause outbreaks in the coming winter. A vaccine which protects against three strains of flu virus is called a trivalent vaccine.

Types of flu vaccine

There are several different types of flu vaccines.

Most flu vaccines are inactivated vaccines. Inactivated means that the virus, or parts of the virus, in the vaccine are not alive, and cannot survive or grow in the body. All of the inactivated vaccines are given as injections.

There is also a live attenuated flu vaccine, which is given as a nasal spray. Attenuated means that the flu virus is alive, but significantly weakened. The live attenuated flu vaccine comes as a nasal spray, and is given to children.

Each year, the UK national flu vaccine programme gives instructions on which type of vaccine should be given to each group of people.

The Department of Health issues advice as to who should be immunised. This is reviewed each year. The aim is to protect people who are more likely to develop complications from flu. People in these groups can get the flu vaccine as part of the national flu programme, free of charge.

For the 2025-26 flu season

Anyone in the following groups can receive the flu vaccine as part of the national programme:

• People aged 65 or older.

• Children aged 2 or 3 years on 31st August 2026.

• Primary and secondary school-aged children (from reception to year 11) and young people who are older than this but remain in a special needs education setting.

• People aged between 6 months and 65 years who have medical conditions that put them at risk from flu, including:

  • Chronic (long-term) lung problems, including asthma and COPD.

  • Chronic heart and vascular problems, including congenital heart disease, heart failure, and ischaemic heart disease.

  • Chronic kidney disease.

  • Chronic liver diseases.

  • Neurological problems, including strokes, multiple sclerosis, cerebral palsy, and severe learning disabilities, including Down’s syndrome.

  • Diabetes and adrenal insufficiency (for example, Addison’s disease).

  • A severely weakened immune system, for example due to chemotherapy or HIV.

  • Conditions that affect the spleen, such as sickle cell disease and coeliac disease.

  • Grade 3 obesity (a body mass index of over 40).

• Pregnant women.

• People in long-stay residential care homes.

• People who are carers for an elderly or disabled person.

• People who are household contacts of people who have severely weakened immune systems.

• Frontline social care workers, if they are unable to get the flu vaccine via their employer.

• People who are homeless.

All frontline health and social care workers, including both clinical and non-clinical staff who have contact with patients, should also be offered the flu vaccine. This is usually given by their employer as part of their occupational health programmes, but, if this is not possible, they may also be able to get it on the NHS.

People who aren’t in any of these groups cannot get the flu vaccine free on the NHS. This is because they are very unlikely to become seriously ill with flu. However, they can pay to get the flu vaccine privately; many pharmacies and private doctors offer this service.

Yes, children can, and should, get vaccinated against flu.

Children who get vaccinated against flu are less likely to catch flu and are less likely to pass flu on to other people, such as elderly relatives. The flu vaccine also protects children against serious illness and death from flu. We often think that flu mainly affects older people but actually children under 5 are almost as likely to be admitted to hospital, including to intensive care units, as people over 65.

Most children are offered a nasal spray flu vaccine. It’s given as a nasal spray into both nostrils. This has been shown to work better for children than the injectable inactivated flu vaccines.

A small amount of purified gelatine, derived from pork, is used in vaccine production though none is actually found in the vaccine itself. Most Jewish and Muslim leaders feel that this does not break religious dietary laws, although there are a range of opinions; some Jewish or Muslim people choose for their child to have the injectable flu vaccine instead but this is less protective for children.

There are some children whose immune systems are not working well (either due to serious illness, such as leukaemia, or due to the treatments of certain conditions, such as arthritis or cancer) who cannot have the nasal flu vaccine. If the nasal flu vaccine isn’t suitable, an injectable flu vaccine can be given instead. Even though it is less effective for children than the nasal flu vaccine, it is usually better than no vaccine at all.

For the 2026 to 2027 flu season

• Children from 6 months to 2 years of age with certain long-term health conditions can get the flu vaccine at their GP surgery.

• Children who were aged 2 or 3 years on 31st August 2026 can get the flu vaccine at their GP surgery.

• Primary and secondary school children (reception to year 11) will get the flu vaccine at school. Home-schooled children, and children not in mainstream education, should be invited for vaccination by the local school-aged immunisation service.

• School-age children with certain long-term health conditions can get the flu vaccine either at their school, or at their GP surgery.

Yes, pregnant women can and should get the flu jab. Pregnant women are at increased risk of becoming severely unwell with flu. They are also more likely than non-pregnant women to be admitted to hospital.

Having flu when you are pregnant may also be associated with serious pregnancy problems, prematurity and lower birth weight for the baby.

The flu jab reduces the chances of this happening. Pregnant women who are vaccinated against flu also pass on some of their immunity to their babies at birth, which lasts for the first few months of their lives.

Your GP (or possibly midwife) should offer you a flu vaccination during your pregnancy if you are pregnant during the flu vaccine period. If they don’t, do ask for one.

If you become pregnant during the flu season you should be offered a flu vaccine as soon as possible.

It’s safe to have the flu jab at any time during pregnancy. There are no known problems from giving the seasonal flu jab to women who are pregnant.

Most people get few, or no, side-effects from the flu jab.

Common side-effects are:

• Soreness, pain, bruising, or redness at the injection site.

• A mild raised temperature (fever).

• Muscle aches.

• A headache.

• Nausea (feeling sick).

• Feeling generally unwell.

These are usually mild and disappear after a day or two.

The injected flu vaccines do not contain a live flu virus. They cannot cause a flu infection.

The live flu vaccine (nasal spray) used for children does contain live, but weakened, flu virus. This is more effective in children than the injected vaccines. The weakened viruses can only grow at colder temperatures inside the nose, and can’t grow in the lungs, or other, warmer, areas of the body. Sometimes, the live flu vaccine can cause a mild runny or blocked nose for a day or two, but it doesn’t cause flu infection in healthy people.

As a precaution, though, the live flu vaccine isn’t given to children with severely weakened immune systems. Children who have very close contact (for example, living together) with people with very severely weakened immune systems (for example, people who have had a bone marrow transplant and are in isolation) should also not be given the live flu vaccine because of the very small risk that they may pass on the virus. Children who can’t have the live flu vaccine can have an injectable one instead.

Serious reactions to the flu vaccine are very rare. Severe allergic reactions (anaphylaxis) occur in about 1 per million people who have the flu vaccine (although it’s thought that the true number might be even lower).

Other, very rare, reactions have been reported after the flu vaccine, such as inflammation of nerves (Guillain-Barré syndrome). The risk seems to be about 1 per million people who have the vaccine. However, there is very limited evidence that the vaccine is directly responsible, and no cases have been proven since 1976. On the other hand there are about 17 cases of Guillain-Barré syndrome in every million people who are admitted to hospital with flu infections.

The flu jab is safe for almost everyone.

The only group of people who shouldn’t have the flu vaccine are people who have previously had a serious allergic reaction to a flu vaccine before, or to one of the ingredients in the flu vaccine. However, it might still be safe to have a different vaccine – ask your healthcare professional.

Some types of flu vaccine should be avoided in certain groups of people. For example, the live flu vaccine shouldn’t be given to children with a severely weakened immune system (for example, children with leukaemia). However, they can still safely have the inactivated (injected) flu vaccine.

Flu immunisation can be given at the same time as other immunisation; it is often given at the same time as the pneumonia immunisation, or Covid-19 immunisations. It is also safe to be given if you are either pregnant or breastfeeding.

What if I have an egg allergy?

Previously it was thought that people with an egg allergy should avoid the flu vaccine. This is no longer the case.

If you’re eligible for an NHS vaccine, you can get the flu jab free at:

• Your GP practice, or a clinic set up by them in conjunction with other local practices. Your GP practice cannot offer the flu vaccine to your child if they are school-aged, unless they have particular medical conditions.

• Schools as part of the flu vaccine programme.

• Your local pharmacy (if they offer this service).

• Your midwife (if they offer it for pregnant women).

• Your employer, if you work in health or social care.

Note: if you have the vaccination somewhere other than your GP surgery, they should notify your GP on your behalf so that it is visible in your notes.

You can also pay to get the flu vaccine privately. Some pharmacies and private clinics offer this service.