That is horrible!!
I have gotten three flu shots in my life and within three days of each shot, became terribly ill. One of the illnesses lasted over a month and I dropped to 90 lbs. (Asian flu) The only times I got the flu was just after a flu shot. Of course, I was politely informed that the shot could never cause the flu, that I was simply unfortunate enough to have caught one that wasn’t included in the vaccine.
I have had probably 15 flu shots over my working career, and then one every year since I retired. I never suffered any illness in the time period after the shot. Never got the flu, either around the time of the shot or afterwards.
A person who gets a flu shot receives dead virus and cannot get the flu from dead virus— because they’re dead and can’t replicate— being dead and all. It takes 2 weeks for the shot to take effect. It is possible to have been exposed around the time of inoculation, prior to becoming immune.
I have read two scientific studies that find that the flu shot isn’t particularly efficacious in seniors, so I will probably stop taking it— even though I get it at no cost through my health plan.