Influenza Vaccination 101


 What is influenza and how will it affect me?

Seasonal influenza, commonly referred to as the flu, is caused by influenza viruses. Symptoms for the condition include sudden fever, chills, body aches, sore throat, cough, and headache. Transmission occurs through respiratory droplets when an individual coughs or sneezes.

Unlike the common cold virus, influenza can potentially cause severe illness and life-threatening complications especially in older people, young children, pregnant women, and those with certain health conditions.

Who should take the influenza vaccination?

The flu vaccine is recommended for all healthy adults, children, frequent travellers, and caregivers.

It is strongly recommended for the following groups of people who are at higher risk of complications:

  • Elderly people above 65 years old.
  • Young children from 6 months to under 5 years old.
  • Pregnant women at all stages of pregnancy.
  • Individuals with chronic medical conditions such as heart diseases, lung disorders, diabetes, kidney failure, or neuromuscular, blood and metabolic disorders.
  • People with chronically suppressed immunity due to disease or long-term medication such as steroids.
  • People who stay in intermediate or long-term care facilities (nursing homes, hostels, etc)

In light of the COVID-19 pandemic, influenza vaccination is also recommended for individuals working or living in closed-living environments.  These groups include:

  • Foreign workers living in all forms of dormitories and private residential premises. In particular, those working in construction, marine and process sectors.
  • Staff working in the following facilities:
    • Custodial and residential facilities, such as homes and shelters
    • Communal living facilities
    • Cruises and ferries
    • Hostels, such as boarding and guest houses

How will influenza vaccination help me in the COVID-19 pandemic?

Infectious disease experts strongly recommend getting a flu vaccination amidst the COVID-19 pandemic. This is because the symptoms of influenza and COVID-19 are very similar and can be challenging to distinguish them. Hence, anyone with flu symptoms will need to be screened for COVID-19 and isolated while awaiting swab test results.

This can put a strain on our nation’s testing resources and healthcare facilities including clinics and hospitals. Flu vaccination helps to reduce such cases and allows preservation of resources to be focused on COVID-19 cases.

Should there be an interval between taking the influenza and COVID-19 vaccine?

A person can be vaccinated with the COVID-19 vaccine even if he or she had received a non-COVID-19 vaccine (e.g. influenza vaccine) within 14 days of the COVID-19 vaccination. An interval of at least 14 days before or after a non-COVID-19 vaccine is encouraged.

What are the influenza vaccines currently available in Singapore?

The quadrivalent influenza vaccine is the most common vaccine to be administered in Singapore. It is often injected into the Deltoid muscle of the upper arm or the outer aspect of the thigh. It is effective against two strains of flu viruses commonly known as Influenza A and B.

The influenza vaccine is released twice a year during the April / May period (Southern Hemisphere, SH) and September / October period (Northern Hemisphere, NH). Each new release incorporates the latest circulating Influenza A and B strains, based on surveillance data from the World Health Organisation.

What is the current recommendation for flu vaccination?

The 2021/2022 NH seasonal influenza vaccine will differ from its previous 2021 SH vaccine in terms of one influenza ‘A’ strain, namely the H3N2 strain. Hence, persons who received the 2021 SH (period May – September 2021) or earlier vaccines (even if vaccination was received less than a year ago), or who have never been vaccinated, should be vaccinated with the 2021/22 NH seasonal influenza vaccine. For optimal protection, vaccination is recommended early in the season.

The NH vaccine can be administered after the SH vaccine at a minimum interval of one month. The current composition of the 2021/2022 NH (egg-based) vaccine is as follows:

  • A/Victoria/2570/2019 (H1N1) pdm09-like virus
  • A/Cambodia/e0826360/2020 (H3N2)-like virus (replaces the “A/Hong Kong/2671/2019 (H3N2)-like virus” from 2021 SH vaccine)
  • B/Washington/02/2019- like virus (B/Victoria lineage)
  • B/Phuket/3073/2013-like virus (B/Yamagata lineage)

 What are some common side effects of the flu vaccine?

Some common side effects include headache, body aches, fatigue, redness, swelling, and pain over the injection site. However, these occur in less than 10 per cent of vaccinated patients are often mild, and will resolve by themselves. 

Are there serious side effects associated with the flu vaccine?

Serious side effects occur very rarely and have a much lower risk compared to severe complications from influenza. However, some risks that may potentially occur include:

  • Allergic reactions leading to rash, low blood pressure, facial swelling and breathlessness.
  • Blood vessel and blood disorders such as lowered platelet levels, blood vessel inflammation, and lymph node swelling.
  • Nervous system disorders, such as fits and progressive muscle weakness (Guillain-Barre Syndrome), that are extremely rare that presents in one in a million cases.

When should I avoid the flu vaccination?

Flu vaccination should be delayed for individuals who are feeling unwell or experiencing a fever. It should also be avoided for those with a known allergy to egg-protein or certain antibiotics such as neomycin / gentamicin, formaldehyde and in individuals who have had a previous serious reaction to influenza vaccines.

Where can I receive the influenza vaccination?

The latest NH influenza vaccine 2021/2022 is available at most Raffles Medical clinics. Alternatively, they can also be purchased online before visiting the clinic.