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FAQs for Parents and General Public

Feature Topic
FAQs for Parents and General Public
FAQs for Parents and General Public
2009-03-31
(V) Influenza and Influenza Vaccination
  1. What is influenza?
  2. Who should receive influenza vaccination?
  3. What kinds of influenza vaccines are there?
  4. What is the recommended influenza vaccine composition?
  5. Does the vaccine cause influenza?
  6. Why does my child need to receive the influenza vaccination?
  7. How many shots of influenza vaccination will my child need?
  8. Why should my child need influenza vaccination every year?
  9. Is my child fit for vaccination if he/she had reaction after the last influenza vaccination?
  10. Can my child receive the influenza vaccination if he/she has received/will receive other immunisation?
  11. Can my child receive the influenza vaccination if he/she is unwell?
  12. My child has asthma, should he/she avoid the influenza vaccination in case it gives him an attack?
  13. Is my child fit to return to school after vaccination?
  14. Is my child protected against influenza once vaccinated?
  15. How long will the protection last after vaccination?
  16. Who should not receive influenza vaccination?
  17. What are the side effects of the influenza vaccination? How to manage these reactions?
  18. Should my child receive influenza vaccine again in coming months if he has already had vaccination in March 2008?
  1. What is influenza?

    Influenza is an infectious disease caused by various types of influenza virus. In Hong Kong, the two subtypes of influenza A virus, H1N1 and H3N2, are most commonly seen. Influenza occurs in Hong Kong throughout the year with seasonal peaks most commonly in February and March, sometimes July and August. The virus mainly spreads by respiratory droplets. The disease is characterised by fever, sore throat, cough, headache, muscle aches, runny nose and general tiredness. It is usually self-limiting with recovery in two to seven days. However, it can be a serious illness to the weak and frail, such as elderly persons, and may be complicated by bronchitis, pneumonia or even death in the most serious cases.


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  2. Who should receive influenza vaccination?

    In 2008-2009, the Scientific Committee on Vaccine Preventable Diseases recommends the following target groups for influenza vaccination in Hong Kong :
    • Elderly persons living in residential care homes
    • Long-stay residents of institutions for the disabled
    • Elderly persons aged 65 years or above
    • Persons with chronic illnesses*
    • Children between the age of 6 months and less than 6 years
    • All pregnant women
    • Health care workers
    • Poultry workers
    Members of the other groups who wish to obtain influenza vaccine for their personal protection can consult their general practitioners.

    * People with chronic illnesses mainly refer to those who have chronic cardiovascular, lung, metabolic or kidney diseases, persons who are immunocompromised, or children and adolescents (aged 6 months to 18 years) on long-term aspirin therapy, and those with chronic neurological condition that can compromise respiratory function or the handling of respiratory secretions or that can increase the risk for aspiration or those who lack the ability to care for themselves.


  3. What kinds of influenza vaccines are there?

    There are two types of vaccines that protect against influenza. The flu shot is an inactivated vaccine (containing killed virus) that is given by injection. A different kind of vaccine, called the nasal-spray influenza vaccine (sometimes referred to as Live Attenuated Influenza Vaccine) is available overseas, but not licensed in Hong Kong.


  4. What is the recommended influenza vaccine composition?

    The viral-strain composition recommended by the Scientific Committee on Vaccine Preventable Diseases in 2008-2009 (northern hemisphere winter) contains the following:
    • A/Brisbane/59/2007 (H1N1)-like virus
    • A/Brisbane/10/2007(H3N2)- like virus
    • B/Florida/4/2006-like virus

  5. Does the vaccine cause influenza?

    Inactivated vaccine cannot cause influenza. However, some people do develop side effects after vaccination.


  6. Why does my child need to receive the influenza vaccination?

    The Scientific Committee on Vaccine Preventable Diseases under the Centre for Health Protection recommends children between the age of 6 months and less than 6 years to receive influenza vaccination to reduce the chance of contracting influenza, its complications and hospitalisation.


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  7. How many shots of influenza vaccination will my child need?

    To ensure adequate immunity against influenza, children under 9 years old who have never received any influenza vaccine are recommended to be given 2 doses of influenza vaccine with a minimum interval of 4 weeks. Those who only received 1 dose in their first year of vaccination are recommended to receive 2 doses in the following year. Thereafter, they need 1 dose each year.


  8. Why should my child need influenza vaccination every year?

    New subtype variants appear from time to time and at irregular intervals which is responsible for seasonal outbreaks. The immunity built up from having influenza caused by one virus strain does not always provide protection when a new strain is circulating. Moreover, the immunity to the disease declines over time and may be too low to provide protection after one year.


  9. Is my child fit for vaccination if he/she had reaction after the last influenza vaccination?

    It depends on the type and severity of the reaction after vaccination. You should consult your family doctor to determine whether the child is suitable for the influenza vaccination.


  10. Can my child receive the influenza vaccination if he/she has received/will receive other immunisation?

    Influenza vaccine is an inactivated vaccine. It does not interfere with the immune response to other inactivated or live vaccines. Influenza vaccine may be given at the same time as other vaccines at different sites.


  11. Can my child receive the influenza vaccination if he/she is unwell?

    The vaccination may be deferred if the child suffers from acute fever on the day of vaccination.


  12. My child has asthma, should he/she avoid the influenza vaccination in case it gives him an attack?

    Asthma is not a contraindication to influenza vaccination with the flu shot. On the contrary, it is a pulmonary condition for which vaccination is recommended because of an increased risk of complications associated with influenza infection.


  13. Is my child fit to return to school after vaccination?

    Your child can return to school as normal if he/she has no reactions which needs attention.


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  14. Is my child protected against influenza once vaccinated?

    The vaccine currently in use helps to reduce the chance of influenza and its complications, but it does not offer 100% protection. It will not prevent "influenza-like" illnesses caused by other viruses. For prevention against influenza, vaccinated children still need to maintain good personal and environmental hygiene, balanced diet, regular exercises and adequate rest.


  15. How long will the protection last after vaccination?

    Normally for one year. Influenza vaccination is required on an annual basis.


  16. Who should not receive influenza vaccination?

    People who are allergic to eggs, neomycin, a previous dose of influenza vaccine or other vaccine components (e.g. neomycin, polymyxin, depending on specific brands of product) are not suitable to have the influenza vaccination. Those with bleeding disorders or on warfarin may receive the vaccine by deep subcutaneous injection. Individuals who suffer from an acute febrile illness on the day of vaccination may receive the vaccine when they recover. People with a history of Guillain-Barré Syndrome developed within 8 weeks after receiving inactivated influenza vaccine should not take the vaccine again.


  17. What are the side effects of the influenza vaccination? How to manage these reactions?

    Influenza vaccine is very safe and usually well tolerated apart from occasional soreness, redness or swelling at the injection site. Some recipients may experience fever, muscle and joint pains, and tiredness beginning 6 to 12 hours after vaccination and lasting up to two days. Immediate severe allergic reactions like hives, swelling of the lips or tongue, and difficulties in breathing are rare and require emergency consultation. If fever or discomforts persist, please consult a doctor. The influenza vaccine may rarely cause serious adverse events such as Guillain-Barré syndrome (1 to 2 cases per million vaccinees), meningitis or encephalopathy (1 in 3 million doses distributed) and severe allergic reaction (anaphylaxis) (9 in 10 million doses distributed).


  18. Should my child receive influenza vaccine again in coming months if he has already had vaccination in March 2008?

    Yes. The viral-strain composition of the influenza vaccine varies every influenza season. Since your son has received the influenza vaccine of 2007-2008 composition, he can receive the influenza vaccine of 2008-2009 composition (northern hemisphere winter) in coming months.