Ideally, set up a meeting with your physician or student health services 2-3 months before your trip.
Most vaccines take time to become effective in your body and some vaccines must be given in a series over a period of days or sometimes weeks.
If it is less than 4 weeks before you leave, you should still see your doctor. You might still benefit from shots or medications and other information about how to protect yourself from illness and injury while traveling.
Check out the Centers for Disease Control and Prevention "Tips for Travelers" website for more information: http://wwwnc.cdc.gov/travel/
For suggested vaccinations for your destination, click on the following link: http://wwwnc.cdc.gov/travel/destinations/list.aspx
Contact Student Health Services to obtain malaria, GI, and HIV prophylaxis in case of exposure.