What Is the Difference Between Trivalent and Quadrivalent Flu Vaccines
Which Flu Vaccine Should You Choose?
What Is the Difference Between Trivalent and Quadrivalent Flu Vaccines?
Influenza vaccination is recommended annually to reduce the risk of seasonal flu infection and its complications. One common question patients ask during flu season is whether they should receive a trivalent or quadrivalent flu vaccine. The difference relates to the number of influenza virus strains included in the formulation. Both vaccines are safe and effective and offer comprehensive protection against currently circulating influenza strains.
Definition: Trivalent and Quadrivalent Flu Vaccines
Trivalent flu vaccines contain three influenza virus strains: two influenza A strains and one influenza B strain.
Quadrivalent flu vaccines contain four strains: two influenza A strains and two influenza B strains.
Both are inactivated vaccines designed to stimulate immune protection against seasonal influenza.
What Is Included in Flu Vaccination?
Flu vaccines are updated annually to match circulating strains predicted for the season.
Trivalent Vaccine Includes:
- Two influenza A strains (commonly H1N1 and H3N2)
- One influenza B strain (B/Victoria lineage)
Quadrivalent Vaccine Includes:
- Two influenza A strains (commonly H1N1 and H3N2)
- Two influenza B strains (both B/Victoria and B/Yamagata lineages)
Both injectable formulations used in Singapore are:
- Inactivated (non-live)
- Administered via intramuscular injection
- Updated yearly based on World Health Organization strain recommendations
The dose per included strain is identical between the two formulations. Both the trivalent and quadrivalent contain the same two A strains, at the same dose.
Why Are Some Clinics Now Using Trivalent Vaccines?
Some health authorities have recommended trivalent vaccines from the 2024–2025 season. This is because B/Yamagata-lineage influenza has not been detected anywhere in the world since March 2020.
With B/Yamagata no longer circulating, the WHO determined that the B/Yamagata component in quadrivalent vaccines was no longer adding meaningful benefit, and recommended transitioning to trivalent formulations.
The quadrivalent vaccine covers all influenza strains currently circulating globally, including both influenza A strains and the active B/Victoria lineage. The additional B/Yamagata component provides a safety net should that strain ever re-emerge.
Who Should Consider Flu Vaccination?
Flu vaccination is generally recommended for:
- Adults aged 65 and above
- Children aged 6 months and older
- Individuals with chronic conditions (e.g. diabetes, asthma, heart disease)
- Pregnant women
- Healthcare workers
- Individuals living with elderly or immunocompromised family members
- Travellers during flu season
It is also recommended for the general public, as vaccination reduces community transmission rates.
Who May Not Need It?
Flu vaccination may not be necessary or may require caution in:
- Individuals with severe allergic reactions to a previous flu vaccine
- Those with known severe allergy to vaccine components
- Individuals who are currently acutely unwell with high fever (vaccination is usually deferred)
Suitability is assessed during consultation.
Benefits of Flu Vaccination
- Reduces risk of influenza infection
- Lowers likelihood of severe illness and hospitalisation
- Helps reduce transmission within households and workplaces
- Supports public health protection during peak flu seasons
Limitations and Risks
- Does not guarantee complete protection
- Effectiveness varies depending on strain match
- Mild side effects may occur (pain at injection site, low-grade fever, fatigue)
- Rare allergic reactions can occur
- Annual vaccination is required due to viral mutation
Flu vaccination does not replace other preventive measures such as hand hygiene and staying home when unwell.
What Happens During the Appointment?
- Registration – Personal and medical details are confirmed.
- Medical Consultation – Medical practitioner reviews medical history, allergies, suitability, and counsels on common side effects.
- Vaccination – Injection administered into the upper arm.
The appointment usually takes 15–30 minutes in total.
How Much Does It Cost in Singapore?
In Singapore, flu vaccination typically costs:
- $30 to $50 per dose for standard quadrivalent vaccines
Prices vary depending on clinic and eligibility for subsidies such as CHAS or MediSave (where applicable).
Frequently Asked Questions
Do I need fasting before flu vaccination?
No fasting is required. You may eat and drink normally before the appointment unless advised otherwise for specific medical reasons.
How long does the appointment take?
The entire visit usually takes about 15 to 30 minutes.
Is flu vaccination safe?
Flu vaccines are generally well tolerated. Common side effects include mild soreness at the injection site or low-grade fever. Serious allergic reactions are rare but should be discussed with a doctor beforehand.
What are the side effects?
Most side effects are mild and temporary. These may include arm pain, fatigue, or mild fever lasting one to two days. Severe reactions are uncommon.
How often should I get the flu vaccine?
Flu vaccination is recommended annually. This is because circulating virus strains change and immunity from previous vaccination decreases over time.
Is the quadrivalent vaccine better than the trivalent vaccine?
Quadrivalent vaccines provide protection against one additional influenza B/yamagata strain which does not seem to be circulating. However, both vaccines aim to reduce the risk of influenza infection and complications.
Is flu vaccination suitable for children?
Flu vaccination is approved for children from 6 months of age. Dosage schedules differ depending on age and prior vaccination history. Children aged 6 months to 5 years are included under Singapore's national immunisation schedule.
Can pregnant women receive the flu vaccine?
Inactivated flu vaccines are generally considered suitable during pregnancy. Vaccination may help reduce flu-related complications in both mother and infant.
If you are considering flu vaccination, services are available at Minmed Clinics. Speak to our doctors to understand which option is suitable for you and your family.
🔗 Find out more about flu vaccination services
Medical Review & Authorship
This page is medically reviewed by:
Dr Yap Jun Jie Julian
MBBS, GDFM
Minmed Group Medical Doctor
The information provided is for general educational purposes and does not replace an individual medical consultation.
Last reviewed: March 2026