Dr Phil Kieran: Does my 11-year-old need a flu vaccine? 

A preteen girl wipes her nose with a tissue because of the flu, a cold, or allergies

My 11-year-old daughter is just over a dose of flu. Will she still need the flu vaccine, or will her immune system fight off the virus?

Flu is a nasty virus. I get a lot of questions every year about who should or shouldn’t get the flu vaccine, and my basic stance is that most people should get it. In Ireland, we recommend that children between two and 17 get the flu vaccine yearly.

The children’s vaccine is live and delivered as a nasal spray in two doses in the first year, followed by a single dose annually.

We need to give the vaccine yearly because the immune response starts to decrease over time, and the strain of flu changes each year. Most kids don’t mind the nasal flu vaccine, and it’s quick to administer.

For those curious about what a live vaccine means, here’s a quick rundown. It is a virus cell that expresses antigens (little protein tags) from the selected flu variants. It is a very weak virus and is grown to thrive in cold temperatures (below body temperature). This means when the immune system meets the virus, it can clear it easily as it can’t replicate and primes the immune system against flu. As the immune system responds to this vaccine, it is normal to have a runny nose, a mild cough, and for the child to feel a little tired, but this is caused by the immune system increasing activity for a few days, not due to illness from the vaccine.

You rightly ask should your daughter get the vaccine when she already has had the flu. My answer to this is yes, she should.

Firstly, unless the diagnosis was confirmed in the lab (which is only done in very few sentinel GP practices), this may have been one of the myriad other respiratory viruses that are around this winter (RSV, adenovirus, parainfluenza, Covid and non-Covid coronaviruses). If this is the case she has no protection from the regular flu.

Secondly, there are multiple flu variants each year (the vaccine covers four specifically), so even though she may have immunity to one, the vaccine will cover another three variants.

The third is to start building up vaccine exposure to the various strains.

Although full immunity to the covered strains reduces over the year, there is evidence that being vaccinated in previous seasons gives some protection in future years.

The best time to get the flu vaccine is before it arrives, so we recommend getting it in September or October. However, there is a definite benefit to getting it up until April, as the flu season here tends to be quite long.

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