According to the Centers for Disease Control and Prevention, the flu vaccine is the best way to protect people against the flu and prevent its spread. The flu vaccine can also reduce the severity of the flu if a person contracts a strain of the flu that the vaccine did not contain. It takes about two weeks following vaccination for antibodies to protect against the flu.
Some dentists do not routinely prescribe antibiotics and still have successful implant cases. Their success rate may increase with using antibiotics, but may not (it is all a matter of odds). You are likely fine, but may consider a different antibiotic with fewer side effects.
In terms of medications, prior to surgery, an antibiotic may be given to prevent infections at the surgical site. Antibiotics are a category of drugs used to combat bacteria, and they are generally given orally (in pill form), or intravenously (through an IV). The selection of the antibiotic depends on the type of surgery a person is having, and its purpose is to prevent an infection at the surgical site.