Cancer drugs
Flu is an infection of the caused by a virus. It is very infectious. Flu is an airborne virus, so it spreads when someone with the virus coughs, sneezes, talks, sings or breathes. This releases tiny droplets into the air. These droplets can reach anyone nearby, and they can get the virus.
The symptoms of flu often come on quickly and include:
a high temperature (fever) or chills
aching muscles and joints
a cough
headaches
extreme tiredness (fatigue)
sore throat
blocked or stuffy nose
Anyone who has flu feels quite unwell. But most healthy people recover within a few days as their gets rid of the virus.
Occasionally people can develop complications from the flu, such as severe chest infections. These are serious illnesses which can need hospital treatment. A small number of people die due to complications.
Cancer or its treatment can lower your resistance to infection. This is called immunosuppression or being . This is because some cancers and cancer treatment can affect how the produces . This can weaken your immune system, making it harder to fight infectious diseases. This makes you more at risk of catching flu.
If you get flu and have low , you are more likely to become very ill. For example, you could develop a complication such as a chest infection (pneumonia).
The flu vaccination makes it less likely that you will catch flu. If you do catch the flu the symptoms will be milder or less severe.
Each year the flu vaccine is updated to include the flu viruses that are circulating that year. This is why every autumn and winter, people at high risk of getting unwell with the flu are invited to have this vaccine.
Adults have the vaccination as an injection into the muscle (intramuscular injection). Children from 2 to 18 years of age usually have a spray vaccine through the nose (nasal). Some children might need to have it as an injection.
Some cancer treatments lower immunity and lower your resistance to flu. These include:
some types of
some treatments
long term
removal of the
a
After cancer treatment, your resistance to infection might be low for some months or years.
Your GP or cancer specialist will usually recommend that you have the flu vaccine if you have a weakened immune system. Depending on your situation, they may suggest you continue with regular flu vaccines once your treatment has finished.
Ask your doctor about the best time to have the vaccine. This will depend on your situation and the type of treatment you are having or have had.
Have the vaccination before the flu virus starts to circulate in the population. This is most likely to happen during the winter months. Flu season in the UK is usually between December and March. It takes up to 14 days for the flu vaccine to work, so it is best to have it before December.
Vaccination clinics usually start in September and continue through to November. You can contact your GP to find out about clinic times. Or you might be able to have it at your local pharmacy. It is still worth having the vaccine after this time if you haven't had it.
Cancer specialists generally recommend that you should have the flu vaccine before you start any cancer treatment. But this isn’t always possible.
For many cancer types, your specialist may advise you to have the vaccine during treatment if you haven’t had one. They will explain when it is best to have this. This might depend on different factors, such as the level of white blood cells in your blood. For example, with chemotherapy, you might have it towards the end of one and just before you start another cycle. The vaccine might not give you as much protection as it would a person whose immunity is not low. But it is still important for most people to have it.
Your specialist may recommend that you do not have a vaccine during treatment if you have a blood cancer. Cancers of the blood include , and . They can let you know the best time to have the flu vaccine.
If you have had a stem cell transplant, your specialist will usually suggest you wait about 6 months before you have the flu vaccine. Again, the length of time will depend on your individual situation.
The flu vaccination is free to people at increased risk of catching flu. This includes people with low immunity due to disease or treatment, such as cancer treatment.
It is also free for:
health and social care workers who have face to face contact with people in care settings
employees if they have a flu voucher from their employer
people who live with someone who has a weakened immune system
people who are main carers
Speak to your GP if you had cancer treatment some time ago and are unsure if you can have a free vaccine. If you are not eligible, you can book and pay for a vaccine at a range of pharmacies or private healthcare providers.
You can read more about the flu vaccination programme where you live:
Wales:
The flu vaccine injection is a non-live vaccine and contains a killed version of the virus. The nasal spray is a live vaccine and contains a weakened form of the flu virus.
The flu vaccine injection is safe for you to have while you are having cancer treatment as it doesn't contain the live flu virus, so you won’t develop flu from having it. Ask your doctor about the best time to have this. This will depend on your situation and the type of treatment you are having.
Some people might not be able to have the flu vaccine. These include people:
with an egg allergy - manufacturers make some of the vaccines from viruses grown in hen’s eggs
who have had a reaction to a flu vaccine before
People with an egg allergy can have a flu vaccine with a very low egg content. Or you can have a different type of flu vaccine grown in cells, not eggs. Ask your healthcare team about this.
Children often have the flu vaccine as a nasal spray. Talk to your child’s healthcare team if your child has cancer. They may suggest that your child doesn’t have the nasal spray if they have a weakened immune system. This is because the nasal spray contains a live, but weakened form of the flu vaccine.
Normally, the flu vaccine helps a child to build up their immunity to flu. But if your child has a weakened immune system, the immune system may not be strong enough to build up a response. Without an immune response, the vaccine virus could cause flu. The doctor might suggest your child has the flu vaccine injection instead.
Side effects can vary from person to person. They also depend on what flu vaccine you are having.
There are several different types of flu vaccine you can have by injection. Your healthcare professional will let you know the one that is right for you.
Here is an overview of some of the very common side effects from the flu injection. Very common means these side effects happen in more than 10 in 100 people (more than 10%). They include:
soreness, swelling, redness, bruising, or hardening of the skin around the injection site
a high temperature or shivering
aching muscles or joints
tiredness
a headache
feeling or being sick
diarrhoea
sweating more than usual
generally feeling unwell
Very common side effects of the nasal spray include:
a runny or blocked nose
loss of appetite
generally feeling under the weather
It is safe to be in contact with people who have had the flu vaccine as an injection if you have a severely weakened immune system.
Children can have the flu vaccine as part of the national immunisation programme. They usually have it as a nasal spray.
If your immune system is severely weakened, for example after having a stem cell transplant, you should avoid close contact with children who have had the nasal spray flu vaccine. This is for about 2 weeks after they had the vaccine. This is because there is a very small chance that the vaccine virus could be passed on to you and cause illness.
If you live with children and you have a weakened immune system, your doctor will advise that they have the flu vaccine as an injection.
Check with your doctor if you are unsure whether your cancer or its treatment has severely weakened your immune system.
Last reviewed: 29 Jul 2026
Next review due: 29 Jul 2029
Your resistance to infection can sometimes be low if you have or have recently had some cancer treatments. There are some vaccinations you shouldn't have when you have low immunity because they could make you feel very ill.
To visit some countries, you’ll need vaccinations before you leave. It’s a good idea to get advice about this at least 8 weeks before you travel.
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