It seems some people with APS have no problems with the Flu vaccine, while others do.
This year, my INR shot up to 7.7.
And, I seemed to have some type of flare. I've been suffering for weeks after the shot.
Professor Shoenfeld in Israel (and others) is doing work on adjuvant syndrome, whereby the flu and tetanus vaccine can trigger APS or cause a spike in antibodies.
When I read about the tetanus vaccine I remembered my teenage migraines and fatigue starting almost immediately after my tetanus vaccination.
The bottom line for me, is that I generally, politely ignore advice proffered by my GPs on APS, preferring only to listen to my excellent Rheumatologist.