Flu (also known as influenza) is a highly infectious illness caused by the flu virus. It spreads rapidly through small droplets coughed or sneezed into the air by an infected person.   For most people, flu is unpleasant but not serious. You will usually recover within a week.

Studies have shown that flu vaccines provide effective protection against the flu, although protection may not be complete and may vary between people. Protection from the vaccine gradually decreases and flu strains change over time. Therefore, new vaccines are made each year and people at risk of flu are encouraged to be vaccinated every year.

The flu vaccination is offered to people in at-risk groups. These people are at greater risk of developing serious complications if they catch flu, such as pregnant women and elderly people.

Who can have the flu vaccine?

The flu vaccine is given free on the NHS to people who:

• are 50 and over (including those who'll be 50 by 31 March 2022)
• have certain health conditions
• are pregnant
• are in long-stay residential care
• receive a carer's allowance, or are the main carer for an older or disabled person who may be at risk if you get sick
• live with someone who is more likely to get infections (such as someone who has HIV, has had a transplant or is having certain treatments for cancer, lupus or rheumatoid arthritis)
• frontline health or social care workers

Flu vaccine for people with long-term health conditions

The flu vaccine is offered free on the NHS to anyone with a serious long-term health condition, including:

• respiratory conditions, such as asthma(needing steroid inhaler or tablets), chronic obstructive pulmonary disease (COPD), including emphysema and bronchitis
• diabetes
• heart conditions, such as coronary heart disease or heart failure
• being very overweight – a body mass index (BMI) of 40 or above
• chronic kidney disease
• liver disease, such as hepatitis
• neurological conditions, such as Parkinson's disease, motor neurone disease, multiple sclerosis (MS), or cerebral palsy
• a learning disability
• problems with your spleen, for example, sickle cell disease, or if you have had your spleen removed
• a weakened immune system as the result of conditions such as HIV and AIDS, or taking medicines such as steriod tablets or chemotherapy

Talk to your doctor if you have a long-term condition that is not in one of these groups. They should offer you the flu vaccine if they think you're at risk of serious problems if you get flu.

Flu vaccine if you're pregnant

You should have the flu vaccine if you're pregnant to help protect you and your baby.

It's safe to have the flu vaccine at any stage of pregnancy.

Find out more about the flu vaccine in pregnancy

Flu vaccine for frontline health and social care workers

If you're a frontline health and social care worker, your employer should offer you a flu vaccine. They may give the vaccine at your workplace.

You can also have an NHS flu vaccine at a GP surgery or a pharmacy, if you're a health or social care worker employed by a:

• registered residential care or nursing home
• registered homecare organisation
• hospice

You can also have the flu vaccine if you provide health or social care through direct payments or personal health budgets, or both.

Who should not have the flu vaccine

Most adults can have the flu vaccine, but you should avoid it if you have had a serious allergic reaction to a flu vaccine in the past.

If you're ill with a high temperature, it's best to wait until you're better before having the flu vaccine.

How effective is the flu vaccine?

The flu vaccine gives the best protection against flu.

Flu vaccines help protect against the main types of flu viruses, although there's still a chance you might get flu.

If you do get flu after vaccination, it's likely to be milder and not last as long.

Having the flu vaccine will also stop you spreading flu to other people who may be more at risk of serious problems from flu.

It can take 10 to 14 days for the flu vaccine to work.

Flu vaccine side effects

Flu vaccines are very safe. All adult flu vaccines are given by injection into the muscle of the upper arm.

Most side effects are mild and only last for a day or so, such as:

• slightly raised temperature
• muscle aches
• sore arm where the needle went in – this is more likely to happen with the vaccine for people aged 65 and over

Try these tips to help reduce the discomfort:

• continue to move your arm regularly
• take a painkiller, such as paracetamol or ibuprofen – some people, including those who are pregnant, should not take ibuprofen unless a doctor recommends it

Allergic reactions to the flu vaccine

It's very rare for anyone to have a serious allergic reaction (anaphylaxis) to the flu vaccine. If this does happen, it usually happens within minutes.

The person who vaccinates you will be trained to deal with allergic reactions and treat them immediately.