I used to get regular flu jabs for a while prior to diabetes as i was considered vulnerable for other reasons, and only ever once had a very bad reaction which they claimed wasn't actually due to the jab, but it put me off having one again for years!
Practice later changed the "vulnerabilty" conditions and I wasn't eligible again until 2013 when I was diagnosed as diabetic. First jabs were fine but the next took ages to get over - I just felt totally under the weather for weeks. However, if I could feel poorly from just a tiny jab, and remembering back to when l did have flu as a young very skinny teenager and lost a huge amount of weight that I couldn't actually afford to lose, I decided that getting a real dose of flu again now could be a major disaster area in combination with my diabetes so I'm continuing to go for my jabs and haven't had any further issues. So on balance for me they're definitely the very much lesser of two evils!
Robbity