Vaccines are available for few disease like malaria but I don't think some preventive medicine for dengue is available.
However, you can take some preventive measures to avoid these disease. Some of the precautions are:
1. Avoid mosquito bite as much as possible.
2. Wear full sleeves cloths especially when going out.
3. Use Mosquito repellent lotion.
4. Spray incest killer spray in your house.
5. Avoid going out in evening etc.
