Flu Season in Singapore: Why Influenza Spreads All Year Round and Why Flu Vaccination Matters

Oct 11

5 min read

Healthcare professional administering an influenza vaccine injection to a patient, highlighting the importance of flu vaccination in Singapore.

Have you ever wondered why everyone seems to be catching the flu at certain times of the year? 🤧

Influenza, commonly known as the flu, follows seasonal patterns around the world. In colder climates, influenza activity tends to increase during winter. People also spend more time indoors and in enclosed spaces, making it easier for respiratory viruses to spread from person to person.

But what about Singapore, where it's warm and humid all year round?

Let's take a closer look at how flu seasons work, why influenza vaccines are updated regularly, and what this means for those of us living in Singapore.

Woman experiencing flu symptoms and blowing her nose into a tissue while sitting in bed, illustrating influenza and respiratory illness during flu season in Singapore.

Northern vs Southern Hemisphere Flu Seasons

Influenza activity follows different seasonal patterns depending on where you live.

In the Northern Hemisphere, including countries such as the UK, China, Japan and the United States, flu season generally runs from October to May, with activity often peaking between December and February.

In the Southern Hemisphere, including Australia and parts of South America and Africa, the pattern is generally reversed.

Flu season typically runs from April to September, with activity often peaking during the winter months of June to August.

These seasonal differences are why healthcare professionals often refer to the Northern Hemisphere and Southern Hemisphere influenza seasons.

What About Flu Season in Singapore?

Unlike countries with four distinct seasons, Singapore sits close to the equator and experiences a tropical climate throughout the year.

However, influenza viruses circulate throughout the year in Singapore, which means you can catch the flu at any time.

Singapore generally experiences two periods of increased influenza activity:

May to August, broadly corresponding to the Southern Hemisphere's winter flu season.
December to March, broadly corresponding to the Northern Hemisphere's winter flu season.

These are typical patterns rather than fixed dates, and influenza activity can vary from year to year.

Factors such as international travel, population mixing and changes in circulating influenza viruses can also influence transmission.

The important takeaway? Just because Singapore doesn't have winter doesn't mean we don't have flu season!

This is why influenza vaccination remains relevant throughout the year.

Why Are Flu Vaccines Updated Every Year?

You may have noticed that influenza vaccines are updated regularly.

That's because influenza viruses are constantly changing.

These changes, known as antigenic drift, can affect how well our immune systems recognise circulating influenza viruses.

To keep up with these changes, the World Health Organization (WHO) monitors influenza activity around the world and reviews vaccine composition recommendations twice a year.

These recommendations are made separately for the Northern and Southern Hemisphere influenza seasons.

Scientists analyse which influenza viruses are circulating and identify the strains most likely to be relevant for the upcoming season.

Vaccine manufacturers then use these recommendations to produce updated seasonal influenza vaccines.

This is one reason why regular flu vaccination is recommended, particularly for individuals at higher risk of influenza-related complications.

Trivalent vs Quadrivalent Flu Vaccines: What's the Difference?

If you've received a flu vaccination before, you may remember hearing about quadrivalent or tetravalent influenza vaccines.

These vaccines were designed to protect against four influenza virus components.

However, influenza vaccine recommendations have changed in recent years.

Current trivalent influenza vaccines contain three influenza virus components:

Influenza A (H1N1)
Influenza A (H3N2)
Influenza B (Victoria lineage)

Previously, quadrivalent vaccines included an additional influenza B lineage known as B/Yamagata.

However, influenza B/Yamagata has not been confirmed in global influenza surveillance since March 2020.

As a result, WHO has recommended removing the B/Yamagata component from seasonal influenza vaccines and transitioning towards trivalent formulations.

Does This Mean Trivalent Flu Vaccines Are Less Effective?

Not necessarily!

It's understandable to wonder whether a vaccine protecting against three influenza components instead of four offers less protection.

However, more components do not automatically mean better protection.

The transition to trivalent vaccines reflects updated scientific evidence about which influenza viruses are circulating.

Since the B/Yamagata lineage has not been confirmed in circulation for several years, including it in seasonal vaccines is no longer considered necessary.

Modern trivalent influenza vaccines are formulated according to WHO recommendations to target the influenza viruses expected to be relevant during the upcoming season.

As with all vaccines, influenza vaccination does not guarantee complete protection.

Effectiveness can vary depending on factors such as the circulating viruses, vaccine match, age and individual immune response.

Nevertheless, vaccination remains an important way to reduce the risk of influenza and its complications.

Should I Look for an Older Quadrivalent or "Tetra" Flu Vaccine?

No, there's no need to specifically seek out an older quadrivalent influenza vaccine.

Current trivalent influenza vaccines follow updated WHO recommendations and are an appropriate option for seasonal influenza vaccination.

If you're unsure which vaccine is suitable for you, speak to your doctor for advice.

When Should You Get Your Flu Vaccination in Singapore?

Because influenza circulates throughout the year in Singapore, there isn't one single vaccination month that suits everyone.

Influenza vaccination is particularly important for individuals at higher risk of developing complications, including:

Adults aged 65 years and above
Young children
Pregnant women
Individuals with certain chronic medical conditions, such as diabetes, heart disease or chronic lung disease
People with weakened immune systems

Annual influenza vaccination is generally recommended for eligible individuals, although some children may require two doses when receiving influenza vaccination for the first time.

If you've already received a flu vaccination earlier this year, you may be wondering whether you need another dose.

The answer depends on factors such as your age, vaccination history, risk factors and the influenza vaccine formulation you previously received.

Your doctor can help determine the most appropriate vaccination schedule for you.

Flu Vaccines Are Now Available at SingMedical! 💉💙

With influenza circulating throughout the year in Singapore, it's always a good time to think about protecting yourself and your loved ones.

We're happy to share that flu vaccines are now available at SingMedical in Clementi!

Whether you're preparing for an overseas holiday, looking after elderly family members, or simply hoping to reduce your risk of catching influenza, our friendly team is here to help.

Not sure whether you're due for your next flu vaccination?

Speak to our doctor, who can advise you based on your medical history, previous vaccinations and individual healthcare needs.

Remember, influenza is more than just a common cold. While many people recover without complications, influenza can sometimes lead to serious illness, particularly among vulnerable individuals.

Taking preventive measures, practising good hygiene and keeping up with recommended vaccinations can help protect you and those around you.