Influenza Vaccination

What is inﬂuenza?

It is a contagious respiratory illness caused by inﬂuenza virus affecting the nose, throat and lungs. It may be mild for some but can also potentially cause serious illness.

How do ﬂu vaccines work?

The vaccine helps in providing protection against ﬂu illness, reduce its severity and risk of hospitalization. It takes about 2 weeks for protection to develop after vaccination. The current vaccine is a quadrivalent vaccine which protect against four strains. As the strains of the virus can change yearly, new vaccine is made to protect against the circulating virus based on expert advice. Hence, it is recommended to be administered on a yearly basis.

How effective are Inﬂuenza vaccines?

Recent studies show that ﬂu vaccination reduces the risk of ﬂu illness by 40%-60% among the overall population during seasons when most circulating ﬂu viruses are well-matched those used to make ﬂu vaccines.

Why do we need to get inﬂuenza vaccine?

Inﬂuenza is a potentially serious disease that may lead to severe illness and hospitalization, or even death. Studies show that vaccination prevented 7 million inﬂuenza illnesses, 3 million inﬂuenza-associated medical visits, 100,000 inﬂuenza-associated hospitalizations and 7,000 inﬂuenza-associated deaths in 2019-2020.

Who should receive inﬂuenza vaccine?

Everyone 6 months and above is recommended to get inﬂuenza vaccine each year. This is especially important to those at risk of complications from inﬂuenza like children aged 6 months to less than 5 years, pregnant women, patient aged 65 years and over as well as people with certain chronic health conditions.

Who should consult health care provider before receiving inﬂuenza vaccine?

People with Guillain-Barré Syndrome (a severe paralyzing illness, also called GBS) or with history of GBS.
People with severe or life-threatening allergy to any ingredient in a vaccine.
People who had severe allergy reaction to previous dose of any other ﬂu vaccine.
People who are feeling sick.

Vaccine side effects

Soreness, redness, and/or swelling where the shot was given
Headache (low grade)
Fever
Muscle aches
Nausea
Fatigue

These side effects are usually mild and short-lasting, especially when compared to symptoms of ﬂu.

Can I get seasonal ﬂu even though I got a ﬂu vaccine this year?

Yes. It is possible to get sick with ﬂu even if you have been vaccinated (although you would not know for sure unless you get a ﬂu test). This is possible for the following reasons:

You may be exposed to a ﬂu virus shortly before getting vaccinated or during the period that it takes the body to gain protection after getting vaccinated. This exposure may result in you becoming ill with ﬂu before the vaccine begins to protect you. (Antibodies that provide protection develop in the body about 2 weeks after vaccination.)
You may be exposed to a ﬂu virus that is not included in the seasonal ﬂu vaccine. There are many different ﬂu viruses that circulate every year. A ﬂu vaccine is made to protect against the four ﬂu viruses that research suggests will be most common.
Unfortunately, some people can become infected with a ﬂu virus that the vaccine is designed to protect against, despite getting vaccinated. Protection provided by ﬂu vaccination can vary widely, based in part on the age and health of the person getting vaccinated. In general, ﬂu vaccines work best among healthy younger adults and older children. Some older people and some people with certain chronic illnesses may develop less immunity after vaccination. Flu vaccination is not a perfect tool, but it is the best way to protect against ﬂu virus infection.

If I had my inﬂuenza vaccine (Northern strain) within 6 months ago, can I get vaccinate again this month?

Yes, you can get vaccinated again this month even if you received the inﬂuenza vaccine (Northern strain) within the last 6 months. The inﬂuenza vaccine is typically recommended one (1) and up to two (2) doses annually because the immunity provided by the vaccine decreases over time, and the strains of inﬂuenza viruses included in the vaccine may change from year to year.

However, it is not recommended for you to vaccinate again this month if you received previous inﬂuenza vaccine in less than 6 months.

What is the difference between Northern and Southern strain vaccine? Should I wait for the Northern strain instead of Southern strain?

For 2024 - 2025, both Southern vs Northern strains are identical. So, it does not matter which strain you are getting during this season. Below is recommendation from World Health Organization (WHO):

I just been infected with Inﬂuenza last 2 weeks. How soon can I get inﬂuenza vaccine and will it be effective?

It is recommended for you to take the vaccine as soon as you have fully recovered from the illness and symptoms. You might have been infected to one of the strains, but this vaccine would be effective and protects you against four strains.

Source: IHH Healthcare Malaysia