Influenza (Flu)
流感疫苗
The yearly shot that cuts your odds of ending up in hospital with the flu.
Vaxigrip Tetra · Fluarix Tetra · Influvac Tetra · FluMist Qu
Influenza is a respiratory virus that circulates in Hong Kong twice a year — a winter peak from January to March and a summer peak from July to August.
The vaccine targets influenza A and B strains specifically, cutting your risk of severe disease, hospitalisation, and death. The composition changes every year because the virus mutates.
Most flu vaccines used in HK are quadrivalent inactivated (QIV) — four strains, killed virus particles, cannot cause flu.
HK CHP recommends seasonal flu vaccination for everyone aged 6 months and above. Priority groups for free or subsidised vaccination:
- People aged 50 and above
- People with chronic medical conditions (any age 6 months+)
- Children and adolescents aged 6 months to under 18 years
- Pregnant women
- Residents of residential care homes
- Healthcare workers
- Poultry workers and pig-slaughtering industry personnel
US CDC recommends annual flu vaccination for everyone 6 months and older. Broadly aligned with HK guidance.
One dose annually. Best taken in autumn before the winter peak (October-November in HK).
Children under 9 who have never had a flu shot need 2 doses, 4 weeks apart, in their first vaccinated season.
Protection takes about 2 weeks to develop after the shot.
| Brand | Manufacturer | HK Reg No. |
|---|---|---|
| Vaxigrip Tetra · QIV inactivated | Sanofi | |
| Fluarix Tetra · QIV inactivated | GSK | |
| Influvac Tetra · QIV inactivated | Viatris | |
| FluMist Quadrivalent · Live attenuated nasal (LAIV) | AstraZeneca |
Most people get nothing or mild reactions for 1-2 days: sore arm, mild fever, tiredness or muscle aches, headache.
Serious reactions are rare. Severe allergic reactions occur in roughly 1-2 cases per million doses.
Myth: The flu shot gave me the flu.
Reality: The inactivated vaccine uses killed virus particles — it cannot cause influenza. Mild immune responses (slight fever, fatigue) for 24-48 hours are not an infection.
Myth: I'm healthy, I don't need it.
Reality: HK CHP data shows unvaccinated children have about 4× the rate of severe flu complications. Healthy people get severely ill from flu too.
See your GP or visit a HK DH clinic. Many private clinics participate in the Vaccination Subsidy Scheme — the government covers $260 per dose for eligible groups.
- HK CHP — Seasonal Influenza Vaccination Programme · HK Centre for Health Protection (HK)
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