Thank you Jxnxlxx for your question.
It's a common question that is posed to us.
A vaccine is essentially a "weakened" form of the virus, it is trying to make your own body immune system react to it. So even if you are already infected before and immune, taking another vaccine would do no harm. (Your body "remembers" these past infections and makes you "immune)
Testing is usually expensive and takes about a week, and even if the test is negative, you could still be immune, because your body stores the "memory" somewhere.
So I would usually advise patients to go ahead and take the vaccine again.
Take care.