Influenza
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Why be immunised against influenza?
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Influenza is a common viral infection of the respiratory tract. The typical “flu-like illness” is a cough, sore throat, fever, headache, and muscle pain. But the infection can vary from a mild cough and cold, to a life-threatening attack of pneumonia. The risk of a severe illness is higher in the very young (less than 6 months old), older people (over 65 years) and those with underlying medical conditions like heart disease, lung problems, diabetes, or suppressed immunity. Epidemics occur in winter (seasonal influenza), and cause about 500 deaths each year. Infection spreads quickly, especially within families and residential institutions (e.g. nursing homes). The incubation period is 1 – 2 days. The infection can be treated by specific anti-influenza drugs if given early in the illness, but it is not easy to distinguish between influenza and the many other viruses that cause similar illness, so treatment based on symptoms is unreliable except at the peak of an epidemic.
When a new strain of influenza virus evolves, it can spread around the world with weeks causing many cases. This is called a pandemic, which may occur at any time of year, and may cause higher rates of severe infection than seasonal influenza.
Immunisation can prevent influenza illness, provided that the vaccine matches the current strains of influenza virus. The level of protection is not as high as with most other vaccines (60-70% protection against seasonal influenza), nor as long lasting, so that vaccination needs to be repeated every year. As well as protecting against illness, vaccination also reduces the spread of infection, which is one reason why it is recommended for health care-workers.
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Which children should have Influenza vaccine and when?
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Children withthe following medical conditions
- Chronic chest disease, including asthma that has required steroid therapy or hospital admission, cystic fibrosis, bronchopulmonary dysplasia (BPD) or other chest illness requiring hospital care
- Chronic heart disease: congenital heart disease, Kawasaki disease, rheumatic fever
- Chronic kidney disease
- Chronic liver disease
- Chronic neurological disease: cerebral palsy, muscular dystrophy,
- Diabetes
- Immunosuppression: immune deficiency syndromes, chemotherapy, splenectomy
The above list is a guide rather than an absolute indication. The decision to start influenza vaccination should be taken with advice from a GP or hospital specialist.
Children under 6 months old are too young to be vaccinated against influenza.
Children aged 6 months to 13 years should have two doses of seasonal influenza vaccine in the first year of vaccination, and one dose per year thereafter. The two doses in the first year should be given 4-6 weeks apart.
Children over 13 years should have one dose of seasonal influenza vaccine in the first year and in the following years. This is because children in the teens are likely to have some immunity already from previous winter epidemics.
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Who should not have Influenza vaccine or should wait?
- Children who have had a life-threatening allergic reaction (anaphylaxis) to a previous dose of influenza vaccine should not have another dose.
- Children less than 6 months of age should not have influenza vaccine.
- Children with egg allergy, because influenza vaccine is made using virus grown on eggs
- Children who are acutely unwell.
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What are the risks from Influenza vaccine?
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A vaccine, like any medicine, is capable of causing serious problems, such as severe allergic reactions.
The risk of influenza vaccine causing serious harm or death is extremely small.
Most children who have influenza vaccine do not have any problems with it.
Mild Problems
- Redness, tenderness, or swelling where the injection was given (up to 1 in 4 of children).
- Fever over 40.5o C (up to 1 out of 20 children).
If these problems happen, they usually start within a day of immunisation. They may last 2-3 days.
Severe Problems (Very Rare)
- Serious allergic reaction (less than 1 out of a million doses).
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What if there is a severe reaction?
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What to look for?
Any unusual conditions, such as a serious allergic reaction or high fever. Serious allergic reactions are extremely rare with any vaccine. If one were to occur, it would most likely be within a few minutes to a few hours after the injection. Signs can include difficulty in breathing, hoarseness or wheezing, a rash like a nettle sting, paleness, weakness, a fast pulse or dizziness.
What to do
- Call a doctor, or take the person to a doctor right away.
- Tell your doctor what happened, when it happened, and when the immunisation was given.
- Ask your doctor, nurse (including health visitor) to report the reaction to the Committee on the Safety of Medicines by a “yellow card”(form at the back of the British National Formulary).
Ask your doctor or school nurse. They can suggest other sources of information and they can obtain more advice for you from the local immunisation co-ordinator or health protection unit.
Last reviewed June 2011.
Last updated June 2011.
