A vaccination, like any other medication, can sometimes cause side effects - fortunately, they are often mild and pass within a few days.
Cats don’t often eat things they shouldn’t, but occasionally curiosity gets the better of them and can lead to a blockage. String, thread, hair bands, rubber bands and tinsel are the most common items to cause a gut blockage in cats.
Having a blocked bladder (being unable to pee) is an emergency and can cause death if left untreated. Contact your vet for an emergency appointment if your cat is struggling to pee.