Covid 19 or flu??

My partner had his flu jab last Saturday 19th Sept and had the usual achy arm at the injection site that day. Yesterday, though he started feeling a bit under the weather with flu like symptoms. Today, 26th Sept and a week after vaccination, he has headache and chills. Is this the mild flu symptoms associated with the vaccine or should we be isolating and applying for a Coronavirus test??

I hope it wasnt Covid..the after effects of the flu jab seem to make us feel off colour. How is he now?