I've had the flu jab for several years together with my son, Philip (25), who has Down's Syndrome so has it as he's considered vulnerable person.
In past years, we've been fine other than the 'punched in the arm' feeling which came a day or two after the innoculation. However, this year, I have felt muscular aches in my arms and legs and a heavy cold-like lethagy. Phil seems to have suffered more than me and has not felt well enough to go to his life-skills day course and social events such as 10-pin bowling. I presume that this is because this year's innoculation is tailored to a different range of the flu strains.
Most people will exaggerate and say that they've had the flu when they've really just had a heavy cold. I once had had the flu which left me bedridden and then housebound for a few weeks. I would happily suffer the current discomfort rather than have a bout of flu which would be far more dangerous to either Philip and myself.