Vaccination Services

What is influenza?

Influenza is an infectious viral disease. It can be caused by various types of influenza viruses. Influenza occurs throughout the year, but is usually more common in periods from January to MarchApril and from July to 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, if persons with weakened immunity and elderly persons get infected, it can be a serious illness and may be complicated by bronchitis, pneumonia or even death in the most serious cases. Serious influenza infection can also occur in healthy individuals.

Why is seasonal influenza vaccination important?

Seasonal influenza vaccination is one of the effective means to prevent seasonal influenza and its complications, as well as reduce influenza related hospitalisation and death.

Who should receive seasonal influenza vaccination?

Given that influenza vaccines are safe and effective and severe cases can occur even in healthy persons, all members of the public aged 6 months or above, except those with known contraindications, should receive seasonal influenza vaccine for personal protection.

HKMC provides the quadrivalent influenza vaccine as recommended by the Scientific Committee on Vaccine Preventable Diseases.

Does the seasonal influenza vaccine work right away?

No. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection.

Is it necessary to get vaccinated against seasonal influenza every year?

Yes. The circulating seasonal influenza strains may change from time to time. In accordance with the circulating strains, the seasonal influenza vaccine composition is updated every year to enhance protection. The immunity built up in a vaccinated person in the prior season will decrease over time and may become too low to provide protection in next season. In addition, the vaccine compositions of 201819 seasonal influenza vaccine are different from those in 201718.

What are the possible side effects of the inactivated influenza vaccine?

Inactivated 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 pain, and tiredness beginning 6 to 12 hours after vaccination and lasting up to two days. If fever or discomforts persist, please consult a doctor. Immediate severe allergic reactions like hives, swelling of the lips or tongue, and difficulties in breathing are rare and require emergency consultation.

Who should not receive inactivated influenza vaccine (IIV)?

People who have a history of severe allergic reaction to any vaccine component or a previous dose of any influenza vaccine are not suitable. Individuals with mild egg allergy who are considering an influenza vaccination can be given IIV in primary care setting, such as health centres or clinics. Influenza vaccine contains ovalbumin (a chicken protein), but the vaccine manufacturing process involves repeated purification and the ovalbumin content is very little. Even people who are allergic to eggs are generally safe to receive vaccination. Those with bleeding disorders or on anticoagulants should consult their doctors for advice. If an individual suffers from fever on the day of vaccination, the vaccination should be deferred till recovery.