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What's in the flu jab?

Approved by our Clinical team | Sep 26, 2022

If you’re considering getting the flu vaccine, but you’d like to know more about how it works and what it contains, read on.

How the flu vaccine is made

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The first thing to understand about the flu vaccine is that there are several different types. The type you get will depend on your age and medical history.

Each year, the World Health Organization (WHO) identifies flu virus strains that will be widespread that season. Information about these strains is released to the manufacturers of flu vaccines, who can then work to tweak their existing vaccines to make sure they offer the right protection.

What the adult flu vaccine contains

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Adults receiving the flu vaccine are given it as an injection, which is why it’s often called the flu “jab”. In this form, the vaccine is always an “inactivated influenza vaccine” or IIV. This means it doesn’t contain any live flu virus.

Many types of IIV are made using fertilised hens’ eggs (“egg-grown”), while others are made using animal cells (“cell-grown”). A third method uses something called recombinant technology.

Because many types of the flu jab are made using eggs, there will often be a small amount of egg in the vaccine.

What the children’s flu vaccine contains

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Children receiving the flu vaccine will usually get the “live attenuated influenza vaccine” or LAIV. This type comes as a spray, and it’s designed to be squirted directly into the nostrils. Although it contains live flu virus, the virus has been weakened, which means it can’t give you the flu.

This type of the flu vaccine also contains small amounts of pork gelatine, so it may not be suitable for all children. The good news is, injectable types of the flu vaccine can be used if LAIV isn’t appropriate or safe for your child.

How can I find out more about what my flu vaccine contains?

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If you want to learn more about the flu vaccine, the best thing to do is talk to your GP or pharmacist. You can also read the Patient Information Leaflet for the vaccines – these are available at the electronic Medicines Compendium (eMC) website.

Three examples are:

Fluenz Tetra (the children’s nasal spray vaccine)
Flucelvax Tetra (a cell-grown vaccine for adults) (QIVc)
Fluad Tetra (an adjuvanted vaccine for those over 65 years)

Is the flu vaccine halal or kosher?

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People who follow certain dietary restrictions due to religious beliefs may be concerned about using the flu vaccine – and in particular, the LAIV nasal spray, which contains pork gelatine.

As stated here, leading figures within the Muslim and Jewish communities have approved the children’s nasal spray for use.

How do I decide which flu vaccine to get?

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You don’t have to decide which vaccine to get – that’s a decision that will be made for you by your health professional. They’ll make sure it’s safe for you and will help you be protected from flu.

Just make sure that when you’re having your appointment, you give all the correct information about your medical history, including any allergies and long-term health conditions.

Is the flu jab safe?

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The flu vaccine is very safe for adults and children. You can’t get the flu from it, although you might experience some mild side effects for a couple of days.

Strong reactions to the flu vaccine are rare. Very occasionally someone might have an allergic reaction known as anaphylaxis. This tends to happen soon after the vaccine is given, which is why all health professionals who give the flu vaccine are trained to administer emergency treatment.

Should I get the flu jab?

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If you’re eligible for a free jab on the NHS this usually means you’re more susceptible to the flu, and more likely to get seriously ill from it. This is why it’s important to get your jab when it’s offered each year.