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2023/24 Quadrivalent Influenza Vaccine Services
The number of influenza cases is likely to increase each year during its peak season. Seasonal influenza vaccination is usually recommended for children and students to reduce hospital admissions and serious illnesses or deaths due to influenza complications. According to the World Health Organization, when the vaccine strains closely match the circulating influenza viruses, the efficacy of inactivated influenza vaccine (IIV) in individuals younger than 65 years of age typically range from 70% to 90%. Adults should be vaccinated and be well-prepared to avoid influenza to protect themselves, their families and friends.
With the relaxation of social distancing measures and entry quarantine policies in various countries, the risk of influenza transmission may also increase as people and tourists no longer mandatory to wear masks in Hong Kong. Given that severe cases do occur in previously healthy persons, all members of the public aged 6 months or above, except those with known contraindications, should receive seasonal influenza vaccination for personal protection. Members of the public can consult their family doctors to receive seasonal influenza vaccination for personal protection.
More About Flu Vaccine
The circulating seasonal influenza strains may change from time to time, the seasonal influenza vaccine composition is updated every year by the circulating strains to enhance protection. Therefore, it is necessary to get vaccinated against influenza every year.
Since it takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection, it is advised to get vaccinated at least two weeks before the start of the influenza season.
Q&A Difference in Inactivated, Recombinant and Live-attenuated Influenza Vaccine
Q: What are Inactivated(IIV), Recombinant(RIV) and Live-attenuated Influenza Vaccine(LAIV)?
The IIV contains inactivated (killed) viruses. It is usually produced by growing the influenza viruses in eggs and is given by injection. Depending on the individual product, most IIVs are recommended for use among persons aged 6 months or above, including those who are healthy, pregnant women and those with chronic medical problems.
Recombinant influenza vaccine (RIV) is produced by growing the influenza viruses in cultured mammalian cells and is given by injection. It contains haemagglutinin (a surface protein of influenza virus) produced by recombinant technology and does not require egg or influenza virus in the production process. It is recommended for use in individuals of 18 years of age or above. A review of existing studies suggested that, in older age group, recombinant vaccines may be potentially more effective than standard-dose inactivated vaccines.
LAIV contains weakened viruses and is given by intranasal spray. LAIV can be used for people 2 to 49 years of age except those who are pregnant, immunocompromised or with other contraindications.
Q&A for Quadrivalent vaccines
Q: When is the influenza season in Hong Kong?
In Hong Kong, influenza is most prevalent in January-March/April and July-August.
Q: How is influenza spread?
The flu is transmitted, or spread, when a person who has the flu coughs, sneezes, or spits, thus sending the droplets with flu virus into the air, where other people may inhale the virus. The virus then enters the nose, throat, or lungs of a person and begins to multiply, causing symptoms of influenza.
Q: Who are the people at high risk for developing complications from influenza?
The following groups are at increased risk for serious complications from or transmission of the flu:
Persons aged >50 years
Children aged 6 months to 5 years
Residents of nursing homes and other long-term care facilities that house persons of any age who have long-term illnesses
Adults or children > 6 months of age who have chronic heart or lung conditions, including asthma
Adults or children > 6 months of age who need regular medical care or had to be in a hospital because of metabolic diseases (like diabetes), chronic kidney disease, obese individuals with body mass index > 30, or weakened immune system (including immune system problems caused by medicine or human immunodeficiency virus)
Children and teenagers (aged 6 months to 18 years) who are on long-term aspirin therapy and therefore could develop Reye’s Syndrome after the flu
Pregnant women at all stages
Healthcare workers and other workers in a healthcare facility including clinics, hospitals and elderly homes
Poultry workers, pig farmers and pig-slaughtering industry personnel
Q: Why do I need to get vaccinated every year?
The circulating seasonal influenza strains change from year to year; hence the influenza vaccine is updated each year to include the circulating strains to enhance protection. The natural protection or immunity you develop after catching a particular strain of influenza virus does not necessarily protect you against another strain of influenza virus. Besides, after you get a flu shot, your immunity to the flu declines over time and may not provide adequate protection after one year.
Q: Can severe problems occur after receiving the influenza vaccine?
Life-threatening allergic reactions are rare. These reactions tend to occur among persons with a severe allergy to eggs, because the viruses used in the inactivated influenza vaccines (IIV) and Live-attenuated influenza Vaccine (LAIV) are grown in chicken eggs. People who have had a severe reaction to eggs or to flu shot in the past, should not be vaccinated with IIV or LAIV before consulting a doctor.
Guillain–Barré syndrome (GBS) is a condition characterized by fever, nerve damage and muscle weakness. GBS can develop following a variety of infections, including influenza. So far, there is no conclusive evidence supporting a causal relationship between seasonal influenza vaccine and GBS.
Q: Can I take influenza vaccine together with other vaccines?
For Inactivated influenza vaccine (IIV) or recombinant influenza vaccine (RIV), they can be given at the same time or at any time before or after other inactivated vaccine (e.g. Pneumococcal Vaccine) or live vaccine (e.g. Measles, mumps and rubella vaccine). Different vaccines should be given with a different syringe and at a different injection site if IIV and other vaccines are given at the same time.
For live attenuated influenza vaccine (LAIV), any other live vaccines should be administered at least four weeks apart.
Government Vaccination Programme (VSS) 2023/24
The Government will provide subsidised seasonal influenza vaccination for the following eligible groups (Hong Kong residents):
Persons aged 50 years or above
Children and Adolescents aged 6 months to under 18 years
Pregnant Women
Persons with intellectual disability
Recipients of disability allowance
Recipients of standard rate of “100% disabled” or “Requiring constant attendance” under CSSA
You may visit the Centre for Health Protection http://www.chp.gov.hk/ website for the latest information of the Vaccination Subsidy Scheme.
