I very strongly recommend the flu jab.
In my first year at university one of my perfectly healthy friends went home for Christmas, caught flu, and died.
My step sister also died of flu a few years ago.
We all automatically get the flu jab every year as that's what's on offer here in the US.
DD did catch flu last year anyway - her boarding school actually ended up closing for a week because so many kids were sick. She'd already had the flu jab, and she also took Tamiflu, and she was better within a few days.