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 include sudden fever, chills, body aches, sore throat, cough, and headache. Transmission occurs through respiratory droplets when a person coughs or sneezes.
Unlike the common cold, influenza can potentially cause severe illness and life-threatening complications especially for older individuals, 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 individuals who are at higher risk of complications:
- Elderly aged 65 years or older.
- Young children from six months to under five 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.
- Individuals with chronically suppressed immunity due to disease or long-term medication such as steroids.
- Children and adolescents aged six months to 18 years old who are receiving long-term aspirin therapy.
- Individuals who stay in intermediate or long-term care facilities such as nursing homes, hospices, and community hospitals etc.
In light of the COVID-19 pandemic, influenza vaccination is also recommended for individuals working or living in close-living environments. These groups include:
- Foreign workers living in dormitories and private residential premises. In particular, those working in construction, marine and processes sectors.
- Workers in the following facilities:
- Custodial and residential facilities, such as homes and shelters
- Communal living facilities
- Cruises or ferries
- Hostels, such as boarding and guest houses.
Read also 5 myths to debunk about flu vaccines
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 upper arm or outer thigh. It protects individuals against two strains of flu viruses commonly known as Influenza A and B.
The influenza vaccine is released twice a year – May for the Southern Hemisphere (SH), and October for the Northern Hemisphere (NH). Each new release incorporates the latest circulating Influenza A and B strains, based on surveillance data from the World Health Organization.
What is the current recommendation for flu vaccination?
The composition of 2022/2023 NH seasonal influenza vaccine (October 2022 to April 2023) is the same as the 2022 SH seasonal influenza vaccine (May 2022 to September 2022). With no change in vaccine composition, annual vaccination is recommended to protect individuals from circulating influenza viruses.
For individuals who have received the 2022 SH vaccine, there is no need for revaccination with the 2022/23 NH vaccine.
The composition of both 2022/2023 NH and 2022 SH (egg-based) vaccines are as follows:
- A/Victoria/2570/2019 (H1N1) pdm09-like virus
- A/Darwin/9/2021 (H3N2)-like virus
- B/Austria/1359417/2021-like virus (B/Victoria lineage)
- B/Phuket/3073/2013-like virus (B/Yamagata lineage)
The current vaccination is hence recommended for (a) individuals who last received influenza vaccine during or prior to the 2021-22 NH season (i.e. before May 2022), and (b) other individuals who have never been vaccinated.
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 side effects occur in less than 10 per cent of vaccinated patients. They are often mild, and will resolve by themselves within a few days.
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. These include:
- Allergic reactions leading to rash, low blood pressure, facial swelling and breathlessness.
- Blood vessel and blood disorders such as lowered platelet levels and blood vessel inflammation, and lymph node swelling.
- Nervous system disorders such as fits, and progressive muscle weakness (Guillain-Barre Syndrome), that are extremely rare and presents only in one in a million cases.
When should I avoid the flu vaccination?
Flu vaccination should be delayed for individuals who are feeling acutely unwell or having a fever. It should also be avoided for those known to have severe reactions to egg-protein or certain antibiotics such as neomycin / gentamicin, formaldehyde, as well as those who have had a previous serious reaction to influenza vaccines.