Many diseases can be prevnted by having vaccines and boosters. Diseases that can be prevented by doing these to include: Influenza Chicken Pox Measles Tetanus Hepatitis C Shingles
"diseases" is a very broad category. It's probably best if you search for specific diseases and then see if they can be prevented from there.
lazyitis !!
Vaccines, quarantines, antibodies, immune system, anti-biotics, gas masks, gloves, washign your hands all the time, and a ton more.