Influenza Vaccine

Influenza vaccines or flu vaccines help to prevent influenza (also known as flu), a common infection caused by Influenza virus types A and B.

​What Is the Influenza Vaccine Used For?

Influenza vaccines help to prevent influenza (also known as flu), a common infection caused by Influenza virus types A and B.

It takes at least 2 weeks for protection to develop after vaccination.

Flu symptoms include fever, chills, headache, feeling tired, muscle aches, sore throat and cough.

Who Should Receive the Influenza Vaccine?

The flu jab or flu shot is recommended for everyone and especially in people who are at high risk of developing influenza complications such as:
  • Elderly aged 65 years and older
  • Pregnant women in any trimester
  • Persons with chronic medical conditions such as diabetes, heart, lung, liver and kidney disease
  • Persons with lower body resistance to infections due to :
    • Conditions such as leukaemia, HIV, spleen removal, or organ transplant
    • Using medications or receiving treatment such as taking long-term steroids, certain cancer drugs or radiation therapy
  • Residents staying in intermediate or long term care facilities
  • Persons aged 18 years or younger and receiving long-term aspirin therapy

What Precautions Should I Follow Before Receiving the Influenza Vaccination?

Inform your healthcare professional if:
  • You are allergic to this vaccine or any of the other ingredients of this vaccine
  • You have a history of Guillain-Barré Syndrome (a rare nerve condition)
  • You have a severe allergy to eggs

How Is the Influenza Vaccination Given?

The flu vaccine or flu shot is either given by injection into a muscle or just underneath the skin.

One dose is recommended yearly as flu viruses are constantly changing, and your body’s immunity to influenza viruses may decrease over time.

What Are Some Side-Effects That I Need to Seek Medical Advice Immediately?

Severe allergic reactions (anaphylaxis) are rare and can happen within minutes to a few hours after vaccination.

The symptoms of a severe allergic reaction include one or more of the following: 
  • Swollen face/eyes/lips/tongue
  • Difficulty in breathing
  • Itchy skin rashes over your whole body
If you experience any of these symptoms, you should inform your healthcare professional immediately. 

What Are Some Other Side-Effects of the Influenza Vaccine?

  • Some people may feel faint after the vaccination
    • Sit for 15 minutes to avoid fainting 
  • Soreness, redness, or swelling at the injection site, slight headache, body aches or tiredness; fever of more than 38oC is not common
    • These side effects usually go away on its own within 2 to 3 days
    • You may take Paracetamol to help to relieve the pain or fever

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

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Influenza Vaccine

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