My dad got the flu shot once for the first when we lived together because he was getting older and having lung issues. I never saw him more sick than that, he was laid out for 2 weeks and sick for at least a month after.

He was retired, never really left the house because I picked up groceries, and our house was tiny and I never got sick. I fully believe that flu shot gave him that sickness, and may have even shortened his life as he died just like 4 or 5 years after that, tho he was very unhealthy.