Post-operative infections following jaw surgery are rare.

It depends on the type of surgery you are talking about. Wisdom teeth extraction usually includes antibiotic coverage to help prevent this. However, in a small number of circumstances, this can happen. Larger, more complicated surgeries often involve hospitalization, but again would have antibiotics. Almost all surgeries carry some risk of infection.

Jaw surgery is very safe and predictable way to correct the malocclusion and the facial deformity. Infections are rare but can occur, since all the incisions are in the mouth and you'll be eating as well. With diligent hygiene and taking precautions after surgery the chances should be very minimal.