Depending slightly on where you are from, yes, you do. Both types of Hepatitis are a risk in all of South America (which depends on region again). Also Tetanus is recommended to get vaccinated against, and a few others depending on destination. See http://wwwnc.cdc.gov/travel.
The Hepatitis A and B combination is best taken 6 months before leaving (3 injections) but provides adequate protection after the first 2 injections, of which the second can be taken after about a month. Tetanus only requires 1 injection. In any case, getting vaccinated on the day you leave provides some protection still, so it is always recommended to get vaccinated, even last minute.
In any case consult a medical professional!