You do not need any particular type of travel immunization to travel to Medellin. Whilst there are mosquitoes here there is no need to take Malaria medication.
If you are planning on going to the Amazon rainforest, however, you should consider getting immunization shots 10 days prior to departure for the following diseases and ailments: Malaria, Hepatitis A, Typhoid, Yellow Fever, MMR, and Tetanus Diptheria. Before your trip, schedule an appointment with your personal physician to go over the details of the immunization of your trip. If you have any more questions or concerns, feel free to check out the website for the Centers for Disease Control & Prevention.